London's transport system was thrown into chaos after attempts were made to set off explosives at four locations, including three Tube stations and on one bus.
The head of the Metropolitan Police said they were intended to kill people.
Eyewitnesses provided accounts of what they saw.
KATE REID, OVAL
I was sitting on the Tube, not paying much attention to anything, and I heard a pop - like a really big balloon had burst - then I saw a little bit smoke.
I saw a bag on the floor next to a young man who looked really scared.
We pulled into the Oval station and he just sprinted away as soon as the doors opened.
The man had a rucksack with him, but whatever had exploded had fallen out of the rucksack and onto the floor.
He was about 20, I think he was black, and really young-looking. He was wearing normal sports clothing, absolutely nothing that made him stand out at all. I would not have noticed him at all if had not been for the bang.
When I left the train at Oval I noticed his bag was still on the train.
SIMON SHIELDS, OVAL
I was sitting a carriage or so away from the device. I heard a bang and saw and smelt some kind of smoke.
The alarm was activated, which was announced by the automatic Tannoy system.
When we pulled into Oval station and the doors opened, there was a lot of shouting and people at the front of the train all got off. I got off and headed for the exit and saw a big blob of yellow "goo" on the floor, near to a black rucksack.
I started to shout for everyone to get off and not to run, many people hesitated. The TfL staff who came to the platform were brave and efficient.
A few of us went to a local bar to talk about what had happened to us.
No-one was injured but many of us were very shocked. I've never hugged so many strangers with such feeling before.
MANISH SUCHDE, SHOREDITCH
Manish Suchde, 42, works near Shoreditch, where the explosion on the bus happened.
We saw the bus stopped outside and everybody running off the bus.
There were quite a lot of people, more than 20.
They were absolutely panicking, they were panicking and distressed.
KIM HOWEY, WARREN STREET
Witnesses said there was a rush to get off the train at Warren Street
I was on the Warren Street Tube when the driver made an unclear announcement. I heard the word 'emergency'.
When the doors opened we heard panicked people towards the front of the Tube screaming and running along the platform towards the back, then running through the passageway to the southbound platform and up the escalator.
As this mob of passengers initially rushed by me, I heard one girl say 'I saw him' while others, many of them young kids, were still screaming and panicking.
Most passengers remained on the carriage, and didn't leave until further announcements were made. As we filed out, we all assumed it was a hyper-sensitive false alarm.
MARK BOND, SHOREDITCH
About 15 people were on board the Number 26 bus and everyone got off safely, said passenger Mark Bond.
I was at the front of the bus and a really loud boom noise came from the rear.
It sounded more of a car crash than an actual explosion. The bus stopped, everyone froze for a couple of minutes before a lady came running down the stairs and said 'I think there's a bomb or something gone off at the back'.
The bus driver immediately opened the doors and everyone rushed out, as did the bus driver. There was a bit of confusion because people were not sure whether it was a small explosion or whether it was a mechanical fault or a car crash.
At the time I didn't think that much of it but obviously now hearing that it was a detonator or some sort of small explosion, it's quite shocking really.
ABENA ADOFU, WARREN STREET
Abena Adofu saw people running into her train carriage
The TV researcher said she knew something wrong when the train was coming into Warren Street and she saw people were running into her carriage.
Lots of people just burst into our carriage and it just became full up with people, I didn't see smoke, I just smelt smoke.
Some people were panicking and screaming.
People still did not know what was going on, some people did try to get on to the train on the opposite platform.
Some people tried to stand around asking and some people just tried to find their way out.
GUY STOCK, SHOREDITCH
Guy Stock was near the double-decker bus in East London when there was an explosion on the upper deck.
It was a Number 26 bus, on its route to Hackney Wick. There was an explosion on the top of the bus.
The driver stopped the bus and got out to look around. On the back seat of the bus, on the top deck, a backpack was found.
Passengers said a funny smell was coming from it, and it appeared to be split.
SOFIANE MOHELLEBI, WARREN STREET
Sofiane Mohellebi smelled smoke while in a Tube tunnel
Paris-born Sofiane Mohellebi, 35, from Walthamstow, said he was on the Victoria Line travelling from Oxford Circus to Walthamstow after attending a job interview. He said he was in a tunnel when he smelled smoke.
He said he has a phobia about using the Underground and this was his first time on a Tube train since the bombings on 7 July.
For a couple of seconds, I tried to see if there was any smoke, people were running towards me from where the smell came from.
One thing was on my mind, is it going to go off.
When the train was in the tunnel it was agonising, there was no way to get to the next carriage. Some people left behind their shoes and their bags of shopping.
Some people said 'do not panic'. In my mind I thought 'why not panic?'
DEAN DUFFY, OVAL
Mr Duffy had just left Oval station when he heard a bang.
As soon as I heard the bang I turned around. I saw people coming out, some were running, some were walking, some were telling other people to calm down and not to panic.
I went straight back, sprinted back and one of the train staff stopped me, said 'don't worry, you know, people are on the way'.
The police turned up within minutes, it seemed like seconds really.
IVAN MCCRACKEN, WARREN STREET
The passenger told Sky News he was in the middle of a train close to Warren Street station when the door to the next carriage burst open and dozens of people rushed in.
Some were falling, there was mass panic. It was difficult to get the story from any of them but when I got to ground level there was an Italian young man comforting an Italian
girl who told me he had seen what had happened.
He said that a man was carrying a rucksack and the rucksack suddenly exploded. It was a minor explosion but enough to blow open the rucksack.
The man then made an exclamation as if something had gone wrong. At that point everyone rushed from the carriage.
AHMED BASIT, OVAL
The 24-year-old bank worker was on his way into Oval station at the time it was being evacuated.
I heard there was white smoke on the train and there was a bag left
on a carriage which led to the evacuation.
They were quite nervous and a bit shocked but nobody was hurt.
PAUL WILLIAMSON, SHOREDITCH
The 19 year old was in a tattoo parlour near the scene of the bus incident.
The first I knew of it there were people running around in the street.
I saw a blonde lady in her 20s who had been on the bus. She was quite scared and shaken and I think she was in a state of shock.
She said it was a minor explosion and there were no injuries but she smelled smoke on the bus.
It can't have been a very loud explosion because we didn't hear anything where we were. The police were very quick, they came in and just said for everyone to get out of the area because there was a possibility of an explosion.
As I came out I saw the bus but it didn't look like there was any damage to it. I didn't see any glass in the street.
INGRID GUION, OVAL
The scene at Oval Tube station after the evacuation
Ingrid Guion was on the train between Stockwell and Oval, on the Northern Line.
I just saw all these people coming towards my carriage and there was a strong smell.
I just thought it was a person, just with the smell, and that people wanted to run away from him.
Then we stopped in Oval and were asked to leave, and then we just had this smell again and I nearly fainted because we couldn't breathe.
Apparently a guy was running away so they tried to catch him. Some people saw him and they saw a small bomb explode in a bag, but it didn't hurt anybody, there was just loads and loads of smoke.
JIMMY CONNOR, WARREN STREET
Jimmy Connor, 32, from Sheffield, left his bag on the train at Warren Street Tube as passengers struggled to leave the carriage. He said they could smell burning, like wiring or a
People were leaving their belongings. Everyone was just waiting for the bomb to go off.
People were trying to make their way to the front of the train.
"I thought I was going to die, everyone else thought the same.
CHRISTINA SAMPSON, WARREN STREET
Ms Sampson was on board the train at Warren Street. She said that overall, people had been "quite calm", and that she had not seen any injuries or damage to the train.
In our carriage suddenly we smelt something like burning rubber and then someone pulled the emergency alarm.
The sirens were going and the Tube pulled in at the station.
The Tube driver then made an announcement but we couldn't quite understand. Some people rushed off the Tube at Warren Street and were kind of screaming and panicking.
There were also lots of people hanging around on the platform waiting to hear what was going on.
I was just in a carriage there was a big bang, it sounded like a balloon had popped but a lot louder, and then we all moved to one end of the carriage.
There was something on the floor, you could see something had exploded.
They opened the door so we could move through into the next carriage and there was a guy just standing in the carriage.
We pulled into Oval and we all got off onto the platform. The guy just ran and started running up the escalator everyone was screaming to stop him.
HUGO PALIT, WARREN STREET
I was going into the station, and I heard a noise. Then I heard noises, like shouting and screaming, and suddenly I saw a guy coming out and people chasing him.
He came out from the station, he was running and he was a little bit confused, looking right and left. I couldn't really catch him because I was carrying two heavy bags, and then he passed by me.
There was another guy who was chasing him.
We saw a policeman, so we waved, like, he was going that way. I don't know if they did catch him or not.
CINDY BUTTS, SHEPHERD'S BUSH
Cindy Butts, Deputy Chair of the Metropolitan Police Authority, was on a bus at Shepherd's Bush when the area was cordoned off.
I was on a bus at Shepherd's Bush and we were all told to get off the bus, the road was cordoned off to the junction of Uxbridge Road and also Goldhawk Road.
Traffic is not coming through. There are lots of police officers around, lots of sniffer dogs.
People from London Transport and of course lots of members of the public are not quite certain what they are meant to be doing and in a state of slight confusion.
It is pretty worrying really because obviously we're close to the BBC where we have had incidents in the past.
There is no one on a loudspeaker informing people of what is going on so they can be a bit more calm and a bit more understanding in terms of recognising that the police are doing a job. I can hear helicopters going above us.