The US military said two more American soldiers had been killed during the clashes, raising the toll to 13 since the fighting flared on Sunday.

The Iraqi parliament's Human Rights Committee has warned that a "tragic situation" is developing in Sadr City, where food and medicine have been running short after a two-week blockade.

Streets empty

Other parts of Baghdad were largely quiet, with the streets empty of cars and trucks after the authorities declared a 5am to midnight (0200 GMT to 2100 GMT) vehicle curfew to prevent car bomb attacks. 

In video

The man who toppled Saddam

Shops, government offices, schools and universities were shut and residents were allowed out only on foot.

Al Jazeera's James Bays, reporting from Baghdad, said the curfew was in place but that sporadic fighting continued.

"The streets are absolutely deserted," Bays reported. "The current Iraqi government is taking no chances at all - the curfew is in place, but it hasn't stopped the violence."

In Tikrit, the hometown of Saddam Hussein, the former Iraqi president who was ousted in the US invasion, a day-long curfew was also in place, according to reports from the AFP news agency.

'US occupation'

Wednesday marked five years since the US-led invasion of Iraq brought down Saddam's government on April 9, 2003.

It took US invading forces just three weeks to defeat the Iraqi leader's forces, with international media showing a group of Iraqis and US marines toppling a statue of Saddam in Baghdad's Firdoos Square.

Your Views

How effective has the US military 'surge' in Iraq been?

Send us your views

The anniversary saw many Iraqis reflect on how their hopes for the post-Saddam era had not been matched by reality, while others took to the street to protest against the continued US presence.

"When I saw the American tanks roll into Baghdad, I was happy and full of dreams ... dreams of a prosperous Iraq, a developed Iraq. But since then it has become a nightmare of suffering and destruction," 25-year-old Sarah Yussef told the AFP news agency.

In Fallujah, where members of the Sunni Arab minority rose up twice against US forces in 2004, several hundred protesters marched through the city calling for American forces to leave.

Muqtada al-Sadr, a populist Shia leader who controls the al-Mahdi Army, had called for a million-strong anti-American demonstration to be held in Baghdad on the anniversary, but later cancelled the protest, saying he feared his supporters might be attacked.

But Jalal Talabani, Iraq's president, hailed the anniversary in a televised address. "April 9 will enter history as the day the most arrogant dictatorship Mesopotamia has ever witnessed was deposed, the fall of a political regime that ... left behind mass graves that contained hundred thousands of innocents," he said.

US troop freeze

Meanwhile, a spokeswoman for George Bush, the US president, left little doubt that he would back a freeze on troop withdrawals from Iraq called for by the senior commander in the country.

Petraeus has called for a pause in the
US troop withdrawal after July [AFP]
General David Petareus told congressional committees that once the last of the 30,000 extra troops sent to Iraq as part of the so-called "surge" leave in July there should be a "45-day period of consolidation and evaluation".

Dana Perino, White House press secretary, said: "You've heard the president say for years that he's the type of commander-in-chief who listens to his commanders on the ground and to the experts who can provide the best advice to him."

Bush is expected to outline his decisions in a public statement on Thursday.

However, Democratic presidential hopeful Hillary Clinton called on Bush to provide an "end-game" for involvement in Iraq.

"I call on the president to answer the question that General Petraeus did not," she said.

"What is our end game in Iraq given the failure of the surge to achieve the objective that the president outlined for it?"