US aircraft have for the first time attacked Saddam Hussein's elite Republican Guard defending Baghdad, as coalition ground troops encountered stiff resistance to their advance on the capital.
Sandstorms are hampering progress
Warplanes and helicopters pounded Iraqi positions guarding the southern approaches, in what correspondents say is a sign that the battle for the city is about to begin.
Eyewitnesses say the sound of the raids - a low rumbling accompanied by flashes which lit up the sky - was very different from earlier ones, suggesting that American B52 bombers had been dropping huge payloads of bombs.
Iraq's Information Minister Mohammed Saeed al-Sahaf said 16 people had been killed and 95 wounded in Baghdad in the past 24 hours.
UK Prime Minister Tony Blair said US and UK forces had now reached Karbala, about 80 kilometres (50 miles) south of Baghdad, and were facing the Republican Guard's formidable Medina division.
He said that coalition forces had already achieved a "huge amount" and vowed that Iraqi resistance would be broken down.
- Thousands of US troops advance through the town of Nasiriya, about 370 km (230 miles) south-east of Baghdad, following protracted clashes with Iraqi forces
- The British military say Iraq's second largest city, Basra, has been designated a military objective in order to get humanitarian aid to its inhabitants
- British Royal Marines move into positions along the Iraqi border with Iran, amid worries that Iran might try to exploit the chaos caused by the war
- British military sources say the southern Iraqi port of Umm Qasr is now "safe and open" after several days of Iraqi resistance
The BBC's correspondent in Baghdad, Andrew Gilligan, says that in one day there have been media appearances by seven top government ministers, designed to show the regime is confident, and that Saddam Hussein is still in charge.
Although Baghdad is relatively quiet with almost no traffic, our correspondent says most of the buildings in the city are unharmed, and electricity and water supplies are working.
The bombardment of the Republican Guard on the southern approaches to Baghdad marks a new phase in the war.
Aircraft have flown more than 900 sorties in the past 24 hours, in what correspondents say is a plan to soften up Baghdad's defenders and try to prevent them retreating into the city itself.
Air strikes targeted the Medina Division, considered to be one of the best and most powerful elements of the Republican Guard.
Pentagon officials say direct attacks by ground forces on Baghdad may be delayed by a few days as bad weather, including sandstorms, closes in.
The BBC's Gavin Hewitt, who is with the 3rd Infantry Division, about 170 km (100 miles) north of Nasiriya, says a ferocious sandstorm has slowed the advance towards the capital.
He says no helicopters can fly, and there is concern that Iraqi irregular forces might use the storm to launch attacks on the stalled convoy.
Iraqi forces, meanwhile, have continued to put up fierce resistance to the American-led attacks.
Another BBC correspondent, David Willis, says the unit he is travelling with south of Baghdad has been stationary for 24 hours, and that Iraqi resistance seems to be growing.
Further south, outside Nasiriya, the BBC's Andrew North has seen a big column of American tanks, light armour and lorries carrying supplies.
He says the Americans have control of the key strategic route across the river Euphrates, but there is what amounts to a guerrilla war in and around Nasiriya.
Correspondents say at least 30 Iraqis, who may have been on their way to reinforce Nasiriya, were killed in what appeared to be a bombing raid.
At least 10 Americans have been killed in fighting in Nasariya since Sunday.
Elsewhere, a second British soldier has died in fighting near al-Zubayr, near Basra in southern Iraq; another British soldier was killed near the town on Monday.
British military commanders say they now regard Basra as a military target, but they say they have no immediate plans to order troops to try to capture the city.
Iraqi troops and irregular militia loyal to Saddam Hussein are reinforcing the city from the north, and are reported to be positioning artillery among the civilian population.
British forces said they destroyed up to 20 Iraqi vehicles, including tanks, which tried to break out of Basra on Monday night
The United Nations Secretary-General, Kofi Annan, has called for urgent measures to help Basra's 1.5 million residents who face the threat of disease from a lack of clean water.
Other key developments
- Iraqi Vice President Taha Yassin Ramadan condemns Arab foreign ministers, saying their call for an "immediate and unconditional withdrawal" of US-led forces from Iraq did not go far enough
- Iraqi Information Minister Mohammad Saeed al-Sahaf dismisses as "lies" US charges that Russian companies have been selling military equipment to Iraq in breach of UN sanctions
- Coalition forces bomb the northern city of Mosul and Iraqi positions on the northern front between Kirkuk and the Kurdish-controlled town of Chamchamal.
- The crew of a US Apache helicopter brought down south of Baghdad are identified as Chief Warrant Officer Ronald Young, 26, and Chief Warrant Officer David Williams, 30.
- Tony Blair is to meet US President George W Bush later this week to discuss the war, say US Government officials