The US military has admitted that stiff Iraqi resistance is slowing the progress of the invasion force as battles rage around strategic towns in the south.
Key areas in southern Iraq remain volatile
The US army's senior ground commander in Iraq, General William Wallace, warned that long supply lines and Iraqi guerrilla-style tactics had reduced the chances of a swift military victory.
"The enemy we're fighting is different from the one we'd war-gamed against," he told The Washington Post, in comments reported to have caused some unease in the Pentagon.
Iraq has said US-led troops will have to fight their way into Baghdad street by street.
"The enemy must come inside Baghdad and that will be its grave," said Iraqi Defence Minister Sultan Hashem Ahmed.
US President George W Bush has said the coalition will fight for "however long it takes" to remove President Saddam Hussein from power.
There was a similar message from UK Prime Minister Tony Blair, who told the BBC that the war to topple the Iraqi leader would take time and have its "tough and difficult" moments.
Explosions were reported on the outskirts of the Iraqi capital on Friday, after one of the heaviest nights of bombing so far.
US officials said two 4,700lb satellite-guided "bunker busting" bombs had been dropped overnight on a key Iraqi communications centre in the city.
The BBC's Andrew Gilligan said the building where he and his colleagues are staying swayed and shook hard.
US bombs killed seven people and injured 92 in Baghdad overnight, the Iraqi Information Minister, Mohammed Saeed al-Sahaf, told a news conference on Friday.
Turning to the situation in Iraq's second city, Basra, the minister said 116 people had been killed there since the war began and another 659 injured.
Meanwhile, in the central town of Najaf, 26 people had died and 60 were wounded during clashes on Thursday, the minister said.
Hundreds of Iraqi civilians are reported to have fled the fighting in Nasiriya, a strategic town in the south, and Basra, also in the south.
In the latest reports from Basra, British military officials said Iraqi militia opened fire on up to 2,000 civilians trying to flee.
They said the Iraqi forces turned mortars and machine guns on the residents and UK forces were returning fire.
Washington has confirmed it is sending up to 120,000 more troops to boost its forces in Iraq - though it insisted the deployments had long been in the pipeline.
Thousands of US reinforcements are already poised to join the battle for Nasiriya, the BBC's Jonathan Charles reports. US forces have spent days trying to dislodge Iraqi troops there.
Other military developments:
US Marines in Nasiriya say they have captured an Iraqi army general, who was picked up at his home
- US cargo planes deliver military supplies and 200 more troops to northern Iraq, a day after hundreds of US troops parachute into the area
- Kurdish militiamen supported by US special forces and air strikes begin a campaign against Islamic radicals in north-east Iraq close to the Iranian border
- Kurdish fighters cross the frontline into Iraqi government-controlled territory, advancing within 20 kilometres of the northern city of Kirkuk
- US troops and members of Iraq's Fedayeen militia units fight a major battle in the central town of Samawah, the site of a crucial bridge on the way to Baghdad.
Iraqi Defence Minister Sultan Hashem Ahmed said he expected US-led forces to surround Baghdad within five to 10 days. US-led forces are already within 80 kilometres (50 miles) of the capital.
But he warned of street-by-street fighting, saying "Baghdad cannot be taken as long as the citizens in it are still alive".
HAVE YOUR SAY
I do not think the coalition was so naive to assume that the war would be a walk in the park
A US military spokesman said air strikes on Thursday night had "taken out" a major communications centre that had been housed in a large tower on the east bank of the River Tigris.
"The strike with two precision-guided munitions was to degrade the ability of the Saddam Hussein regime to command and control the actions of Iraq's military forces," a US military spokesman in Qatar told the BBC.
A telephone exchange in one of Baghdad's main shopping areas was left a smouldering wreck and another telephone building was damaged.
But BBC correspondents in the city say many phones still seem to be working.
In other developments
The UK ship Sir Galahad, carrying 650 tonnes of much-needed food and water for Iraqis, arrives at the southern port of Umm Qasr
- The United Nations reaches broad agreement on restoring the oil-for-food programme in Iraq
- Iraqi television broadcasts interviews with three Iraqis arrested on suspicion of spying for the US
- Iraq denies that two dead British soldiers shown on Arabic television on Wednesday had been executed
- Russian President Vladimir Putin calls for an immediate end to the war