Italy has sent 3,000 soldiers; Poland has sent 2,400 and El Salvador has about 380 troops in Iraq.

Bush and the three other leaders "reaffirmed their shared commitment to helping the Iraqi people realize a free and democratic future," said White House spokesperson Scott McClellan.

Speaking to the British Broadcasting Corporation Friday, British Foreign Secretary Jack Straw said the "lid of the pressure cooker has come off."

"There is no doubt that the current situation is very serious and it is the most serious that we have faced," said Straw.

British Prime Minister Tony Blair, UN Secretary General Kofi Annan and Bush will meet next week to discuss the violence.

U.S. forces continued to battle armed insurgents across the country on Friday, a day that marks a year since a crowd toppled a statue of Saddam Hussein in a Baghdad square.

Marines battled to take Fallujah from Sunni fighters, while other troops fought to put down a recent uprising of Shiites to the south.

In the centre of Baghdad, an explosion shook the area near Firdos Square, where the statue was pulled down last April.

• FROM APRIL 9, 2003: Saddam's birthday statue toppled
  

A mortar shell damaged a small building next to two hotels where many foreigners are staying. The damaged building and the hotels stand inside a barricaded compound guarded by U.S. forces.

Earlier Friday, U.S. troops warned that Shiite militants might carry out bomb attacks near the square. An armoured car drove around the square issuing warnings over a loudspeaker that a curfew was to be imposed, and anyone seen with weapons would be shot.

Shops were closed in Baghdad and there was little traffic on Friday.

Gunmen roamed freely along the highway near the western entrance to Baghdad on Friday. A tanker truck attacked and destroyed there sent a cloud of smoke over the city.

Fallujah offensive briefly halted

To the west of Baghdad, U.S. marines briefly stopped their efforts to take over Fallujah on Friday to allow humanitarian aid into the area.

U.S. marines fire mortar shells on the outskirts of Fallujah on Friday. (AP Photo)

"As of noon today coalition forces have initiated a unilateral suspension of offensive operations in Fallujah," said Paul Bremer, the top U.S. administrator in Iraq.

About 90 minutes later, Lt.-Col. Brennan Byrne, a marine commander, said his forces had been cleared to resume those offensive operations.

Fallujah residents lined up at checkpoints as they tried to leave the city during the pause in fighting, said Byrne. Overnight, troops had used loudspeakers to tell people that women, children and old men would be allowed to leave.

The marines have been laying siege to Fallujah, a hotbed of Sunni militants opposed to the occupation, since Monday. Fighting in the streets this week has killed more than 280 Iraqis and four marines.

• FROM APRIL 4, 2004: Mosque hit by missiles, 40 dead
  

On Thursday, the marines said they had taken about one-fourth of the city, which has a population of about 200,000.

U.S. takes back Kut from Shiite fighters

To the south, U.S. troops encountered little resistance as they fanned out across Kut, a city Ukrainian soldiers pulled out of on Wednesday after battling with Shiite militias there.

Fighters with the al-Mahdi army, led by radical Shiite cleric Muqtada al-Sadr, have been clashing with troops from coalition allies since last weekend.

By midweek, the Shiite militias had taken control of Kufa and large portions of Najaf.

In the other cities, Iraqi police have abandoned their posts or simply stood aside as the al-Mahdi gunmen roam the streets.

Canadian among hostages

Al-Sadr and his followers had nothing to do with a series of kidnappings this week in Iraq, said a senior aide to the cleric.

"We condemn such acts and we pray for their release," said Amer al-Husseini, the cleric's representative in the Sadr City district of Baghdad.

A Canadian human aid worker was among at least six foreigners kidnapped by militants in southern Iraq.

Fadi Ihsan Fadel was taken hostage by militants in Najaf, where he was working with the New York-based International Rescue Committee.

Militants holding three Japanese civilians – two aid workers and a journalist – say they'll burn their captives alive unless Tokyo pulls its troops out of Iraq.

Japan's Prime Minister Junichiro Koizumi said the 530 troops currently in southern Iraq on a noncombat mission to help in reconstruction will stay there. Japan has plans to send several hundred more soldiers.

Two Arabs from Jerusalem in Iraq as aid workers were also kidnapped.

Palestinian leader Yasser Arafat made a personal appeal for their release.

Allies not backing down – yet

The government in Seoul said it wouldn't be deterred from its plan to send 3,600 troops to Iraq, but doesn't want its civilians going to the country.

Thailand said on Thursday it might consider removing its 443 troops if the security situation deteriorates further. Its troops are assigned to the southern city of Karbala until autumn.

Australia said pulling its 850 soldiers out now would be "cutting and running."

Canadian Prime Minister Paul Martin said on Thursday that Canada wouldn't be able to help out in a meaningful way militarily in Iraq even if it were asked.

Commitments in Afghanistan and elsewhere have simply tapped out the military's capability to respond, he said.

Written by CBC News Online staff