Kelly Sotherton is in third place after four events in the heptathlon at the World Championships while team-mate Jessica Ennis slid to fourth.
Marlon Devonish, Mark Lewis-Francis and Craig Pickering all reached Sunday's 100m semi-finals while Phillips Idowu booked a spot in the triple jump final.
The first gold medal in Japan was claimed by Luke Kibet in the marathon while Reese Hoffa won shot put gold.
Jo Pavey finished fourth in the 10,000m which was won by Tirunesh Dibaba.
ACTION AS IT HAPPENED (ALL TIMES BST):
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1441: That's your lot for today. By the time you wake up on Sunday morning Andrew Lemoncello will already have done his stuff in the 3,000m steeplechase heats and Christine Ohurogu - among others - will have competed in the 400m heats.
Ennis, Sotherton and Kluft resume hostilities at 0915 on Sunday in the long jump, followed by the javelin - Sotherton's least favourite event - and the 800m at 1345.
Pick of the day is Powell v Gay in the 100m, with the semi-finals at 1210 and the final at 1420. Which of the three Brits through to the semis will make it to the last eight? We'll find out in the morning.
1429: At the bell, Tirunesh Dibaba takes the lead and Jo Pavey goes into third. Urgh but she is overtaken by American Kara Goucher coming round the final bend. Ethiopia's Dibaba retains her title in 31:55.41 ahead of Turkey's Elvan Abeylegesse. Pavey has to settle for fourth.
"It is a brave, brave run from Jo Pavey which should have been rewarded with a medal. Fourth again - and out of the medals. She will be tired but will be so, so disappointed to have run a brilliant race but come away with nothing again. She went for it with all her heart but just did not have enough pace at the end."
BBC pundit Steve Cram
1426: "Jo Pavey will say these are people I know I can beat. I just have to work hard and stay involved now."
BBC pundit Steve Cram
And Jo Pavey moves into four place with two laps to go ... Come on ...
1424: Five laps to go. Pavey is in seventh or eighth place, while Elvan Abeylegesse strings it out in the lead. Pavey moves up into fifth - the BBC's Brendan Foster excitedly says a medal beckons for the Briton.
1417: Dibaba takes on some water and after hanging at the back for a bit, she accelerates round to the middle of the field. Britain's Jo Pavey is still in the middle - it is getting pretty sticky out there in the humid conditions, but the pace is picking up now as the runners come through 7,000m.
1417: I spoke too soon, here's Crammie: "What's wrong with Dibaba? She is holding her stomach and she is 10m off the pack. Let's keep an eye on this."
1408: Ooops Japan's Kayoko Fukushi has to stop running because her shoe has come off. The pace is so slow that she manages to catch up with the group. Shortly afterwards Benita Johnson and Mestawet Tufa bump into each other and fall down. Other than that, nothing is happening
1410: "Belgian Nathalie de Vos is at the front but nobody is remotely interested in picking up the pace. Jo Pavey is just sat at the back but it's just ticking along at the moment. But soon the gameplans will be coming into action."
1408: No-one can get near the big man Reese Hoffa so he claims shot put gold with his throw of 22.04. So shirt-throwing fellow American Adam Nelson takes silver with Belarussian Andrei Mikhnevich in third.
1401: The women's 10,000m will bring down the curtain down on the opening day of competition in Japan. The runners are through 1200m now and Britain's Jo Pavey is nicely nestled in the pack. The big favourite though is Ethiopia's defending champion Tirunesh Dibaba.
1347: Jessica Ennis produces a brilliant 200m to win the event and bring a close to the heptathlon after four events on day one. The Briton hit her groove off the bend and ran a personal best of 23.15. Kelly Sotherton also set a personal best of 23.40 in the 200m as she finished third behind Carolina Kluft. And we'll have the standings as soon as the official bods have got their calculators out.
"I'm impressed with how Jessica handles herself because she was just in control in this race. Kelly went off hard as she knows Jessica has a strong finish, but it was brilliant running from both of them."
BBC pundit Denise Lewis
1336: Reese Hoffa pumps his fists and roars his appreciation as he extends his lead in the shot put with a throw of 22.04m. This piece of news may not please everyone, however:
"When will the IAAF realise that nobody cares about the shot put and take it out of the championships?"
Icelandic-superlion on 606
1331: Phillips Idowu reaches Monday's triple jump final; his first round effort of 17.07m is good enough to go through. But the Londoner, who has been struggling with a back injury, tells BBC Sport that he has been getting a bit of stick from his fellow competitors.
He said: "Everyone has been like 'I thought you was hurt man' and I've been saying 'I am hurt, I am hurt, my back's hurting right now'".
1324: Felix Sanchez of the Dominican Republic showed glimpses of his past form as he was the fastest qualifier in the 400m hurdles in 48.70 seconds. The Olympic champion has been struggling with injury since the Athens Games but looks like he could be in the mix again. He was followed home in the last heat by defending champion Bershawn Jackson.
1317: Coming up in Osaka, we have the 200m in the heptathlon and the women's 10,000m final, where Jo Pavey makes her championship debut. Also keeping an eye on Mr Idowu too.
1304: Uh-oh, the arrow of gloom comes out as Dale Garland fails to go through in the 400m hurdles. The Briton finishes last in his heat in 49.98 seconds.
1302: "I predict Marlon is the only Briton who is going to reach the 100m final - if Mark Lewis-Francis does then I am knowledgeless about athletics."
Laouane on 606
1252: American Reese Hoffa lets out a huge roar and struts round the shot put circle after landing 21.81m to take the lead in the final. BBC commentator Paul Dickenson describes him thus: "He's six foot tall and six foot wide".
There are more histrionics in the circle when defending champion Adam Nelson throws down his shirt to psyche himself up, before throwing 21.47m for second.
1250: Out on the track, the men's 400m hurdles heats are under way, where Britain is represented by Dale Garland. The Guernsey athlete used to be a decathlete but is now focusing on the hurdles.
1245: Here comes Idowu - and he's gone back to the bleached close-cropped barnet. The qualifying standard for Monday's final is 17.10m and Idowu comes out with 17.07m at his first attempt. An encouraging start.
1240: In the field, qualifying for the men's triple jump final is under way but no sign of Phillips Idowu yet. The men's shot put final is also in the very early stages. Idowu, the Commonwealth champion, says he wants to "pull out a shocker," - so let's see if he, er, can.
1231: Mark Lewis-Francis runs a season's best 10.17 seconds to join Devonish in the semi-finals. Craig Pickering recovered from a poor start to win the final quarter-final in 10.21. So all the British sprinters are through. Let's have another arrow to celebrate.
1222: Marlon Devonish is safely through to Sunday's semi-finals too as he finishes second to Tyson Gay, who is the fastest man in the world this year. Devonish is through in 10.13, while the American clocks 10.06.
"Marlon looked very relaxed and that's not something we usually see from him. He went through his own phases, ran his own race and was not influenced by the athletes around him."
BBC pundit Michael Johnson
1217: Well, the answer is he looked much, much better. The Jamaican world record holder wins the first quarter-final in 10.01 seconds - and even watches himself on the big screen whilst he runs it too.
1215: The 100m quarter-finals are about to get under way again and here's what BBC pundit Michael Johnson had to say about Asafa Powell in the first round: "He looked really weird - he looked like he couldn't hold it together." What can he do now?
1210: Here's the latest heptathlon standings and it's mixed news for the Britons. Jessica Ennis has dropped from second to sixth place but Kelly Sotherton has moved up from fourth to third behind Carolina Kluft and Lyudmila Blonska. Just the 200m to go today.
1156: Bad news for Jessica Ennis as she is below par in the shot put. She can only manage 11.93m and that is sure to mean she will slide down the standings. Sotherton does better with her second throw of 14.14m while Kluft lands a season's best 14.81m. We'll let you know the standings when the officials have totted up the points.
1152: And that's a hat-trick. All three British female 800m runners go through to Sunday's semi-finals as Jemma Simpson also finishes second in her heat to go through in 2:00.47.
"That really is a mark of the strength and depth that we have in this event. Semis will be tough but they all have a chance."
BBC commentator Steve Cram
1146: Jenny Meadows lets her elbows do some of the talking as she runs an aggressive race to join Okoro in the 800m semi-finals. She sets a new personal best of 2:00.14, as she finishes behind three-time champion Maria Mutola.
1134: The first track action of the night sees Britain's Marilyn Okoro run a tidy race to reach the 800m semi-finals. After getting trapped on the inside the 22-year-old Londoner came through strongly in the final 20m to qualify in 2:01.78.
"This season I haven't run the most confident of races but I'm getting there now and I've come here to get the performance that I know is in me," Okoro told the BBC Sport.
1134: The 2000 Olympic heptathlon champion Denise Lewis has some encouraging words for the 21-year-old Ennis. She tells the BBC: "It was a fabulous hurdles race for Jessica. She is looking lean and strong - and I think she can go faster."
1127: The heptathlon is under way with two groups out in the shot put circles. Ennis lands 11.88m with her first attempt but Sotherton goes further, landing a season's best of 14.02m with her first throw. Kluft, who is in the same group as Sotherton, marks up 12.88m.
1120: "I can't see Kelly Sotherton or Jessica Ennis beating the almost unstoppable Carolina Kluft but they may be bronze or silver medal hopes."
United_tillidie on 606
1107: "With Christian Olsson out of the triple jump, here is an opportunity for Phillips Idowu to produce something special. It's such a gruelling event because of the strain it puts on your body and so I'm keeping my fingers crossed."
BBC pundit Colin Jackson
1100: A quick sweep of the Britons in action just before the action resumes in Osaka. Jessica Ennis and Kelly Sotherton have the shot put and 200m to come in the heptathlon while Marlon Devonish, Mark Lewis-Francis and Craig Pickering go in the 100m quarter-finals.
Jemma Simpson, Marilyn Okoro and Jenny Meadows begin their 800m campaigns, Dale Garland goes in the 400m hurdles heats, Phillips Idowu aims to get into the triple jump final while Jo Pavey contests the 10,000m final.
1045: Late risers amongst you will have missed out on an interesting opening ceremony in Osaka with acrobats doing tumbling tricks.
Jessica Ennis was in action in the heptathlon, winning the hurdles and clearing 1.89m in the high jump to lie second so far.
It's still very early days, but what are the chances of her hanging onto a podium spot with six events to go?
Tyson Gay and Asafa Powell eased into the 100m quarter-finals - well, Powell looked a little too relaxed in his heat. Marlon Devonish was the fastest man through in 10.13 while Mark Lewis-Francis and Craig Pickering also reached the next round, which takes place at 1215.