Twenty-three people were killed and 83 injured in Baghdad's Shi'ite slum of Sadr City on Wednesday, security sources said, despite vehicle bans aimed at preventing unrest from spreading on the fifth anniversary of the fall of Baghdad.

Up to 73 people have died in Sadr City since Sunday in battles between black-masked militia loyal to cleric Moqtada al-Sadr and U.S. and Iraqi troops.

The upsurge in fighting comes as the top U.S. officials in Iraq testified in Washington that they opposed setting a timetable to withdraw troops from the 5-year-old war.

"The floor of the hospital is covered with the blood of children," said Dr Qasim al-Mudalla, manager of the Imam Ali hospital in Sadr City, where he said four children and two women were among 11 dead bodies brought in on Wednesday.

"What is the world doing? They have seen the blood of our children and are doing nothing."

Other parts of Baghdad were quiet, with streets clear of traffic because of a one-day vehicle ban in the capital for the anniversary of the day U.S. troops rolled into the capital, deposing President Saddam Hussein.

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

Sadr had called a mass demonstration against the United States for the anniversary, but postponed it saying he feared for his followers' safety.

Many Iraqis spoke of the anniversary with bitterness. Retired army officer Salim Hussein said the past five years had yielded nothing but "blood, bombs, curfews and in-fighting."

"The government is totally incapable of providing security," he said, walking near the square where U.S. forces toppled Saddam's statue on April 9, 2003.

President Jalal Talabani, however, hailed the anniversary in a televised address as a day to be celebrated.

"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.

U.S. President George W. Bush, who is due to give a speech on Iraq on Thursday, spoke to Prime Minister Nuri al-Maliki by telephone. Iraqi government spokesman Ali al-Dabbagh said Bush expressed support for Maliki's crackdown on militia.

U.S. DEATHS

Maliki launched operations against Sadr's militia last month in the southern city of Basra and fighting has spread to Baghdad, where the cleric's Mehdi Army has clashed fiercely with both U.S. and Iraqi troops.

U.S. forces announced on Wednesday that four more American soldiers had died, raising the toll to 15 since an upsurge of fighting began on Sunday. Rockets or mortars, which U.S. forces say are mainly fired from Sadr City, hit the Green Zone compound but caused no injuries, the U.S. embassy said.

The Iraqi parliament's Human Rights Committee warned in a statement of a "tragic situation" in Sadr City, where food and medicine are running short after a two-week blockade.

Vehicle bans were also imposed in Samarra and Tikrit, Saddam Hussein's hometown. In Falluja, where members of Saddam's Sunni Arab minority rose up twice against U.S. forces in 2004, several hundred protesters marched calling for American forces to leave.

In Washington, the top two U.S. officials in Iraq testified to members of Congress for a second day.

Military commander General David Petraeus and ambassador Ryan Crocker said Iraq had made progress over the past year, but the improvements were fragile and could be reversed.

Petraeus advised against committing to a timetable for new troop reductions after forces sent last year as part of the so-called surge return home in July.

Petraeus' testimony suggests more than 100,000 U.S. troops will still be in Iraq when the next U.S. president succeeds Bush in January. Republican candidate John McCain opposes a timetable for further troop cuts, while Democrats Hillary Clinton and Barack Obama want to set a timetable to withdraw.

The U.S. State Department said Secretary of State Condoleezza Rice will go to Bahrain and Kuwait to discuss the Israeli-Palestinian peace process and Iraq, focusing on ways Iraq's neighbors can participate in Iraq's development.

Rice's first stop will be Bahrain April 21 to meet foreign ministers from the Gulf Cooperation Council as well as Egypt and Jordan, department spokesman Sean McCormack said.

In New York, the Associated Press said that an Iraqi judicial committee has ordered the release of one of its photographers held by the U.S. military in Iraq for two years, and dismissed terrorism-related accusations against him.

The AP said a four-judge panel ruled that the case of Bilal Hussein, an Iraqi, falls under a new amnesty law and ordered Iraqi courts to "cease legal proceedings" and release him.

Tens of thousands of Iraqis and more than 4,000 U.S. troops have died in the war. Two million Iraqis have fled the country and about as many are displaced within Iraq.