BAGHDAD, Iraq — Gunmen fired on supporters of the radical Shiite cleric Muqtada al-Sadr yesterday, killing one person and wounding two others as they made their way to protests planned for the second anniversary of the fall of Baghdad to U.S.-led troops.

In the poor New Baghdad neighborhood, meanwhile, four children were killed when they came across explosives while digging through garbage for scrap metal, witnesses and police said. It was unclear what caused the blast.

"It's really ironic," said Qais Mousa, who saw the explosion. "We are living in a rich country, while these poor innocents are dying in this horrible way."

Also yesterday, a bomb killed a U.S. soldier near Hawija, 150 miles north of Baghdad, the U.S. military said. It also reported that a Marine died Wednesday in a motor-vehicle accident during combat operations in Fallujah, 40 miles west of Baghdad. No other details were provided.

After dark yesterday, al-Sadr supporters marched and chanted through the city, hanging anti-U.S. banners on columns surrounding Firdos Square, where a statue of Saddam Hussein was pulled down on April 9, 2003, as U.S. troops spread through the capital.

Al-Sadr had urged his supporters to gather today at the square, and a group was at the landmark along with police after the 11 p.m. curfew. U.S. and Iraqi officials said they were preparing for the demonstration.

The cleric had stayed out of the limelight since his Mahdi Army militiamen accepted truces last year after failed uprisings in the southern city of Najaf and Baghdad's Sadr City neighborhood. But he has stepped up criticism of the United States in recent weeks, mostly by organizing today's protest.

Sunni Muslim clerics also called demonstrations today to demand that American and other foreign troops leave Iraq.

Sheik Hassan al-Edhari, an official at al-Sadr's Baghdad office, said al-Sadr's mainly Shiite followers want the new Iraqi government to set a schedule for pulling out foreign troops and for putting Saddam on trial.

During his sermon yesterday in the capital, the head of an influential Sunni group accused coalition forces of "killing the Iraqi people daily."

"We demand that the occupation troops withdraw from Iraq. We don't want them to do it immediately, but we want them to set a timetable for their withdrawal," said Sheik Harith al-Dahri, whose Association of Muslim Scholars is believed to have ties to Iraq's insurgents.

At another Sunni mosque in Baghdad, Sheik Ahmad Hasan al-Taha instructed worshippers to refrain from marking the April 9 anniversary. Al-Taha also called for the release of arrested religious figures, claiming there were more than 90 imams in detention.

U.S. military officials said they had nothing planned to mark the anniversary, and refused to comment on security measures. But additional Bradley Fighting Vehicles and Humvees were seen in areas where demonstrations were expected.

The Iraqi army said three masked gunmen killed an Iraqi army officer, Maj. Mahmoud Hassan al-Yassiri, late Thursday in the southern city of Basra.

In the Shiite holy city of Najaf, four civilians were injured by a bomb that exploded near a bus station, police Capt. Qussai al-Jazaeri said.

In another incident, the U.S. military said yesterday that a cameraman carrying CBS press credentials was detained in Iraq this week on suspicion of insurgent activity. The cameraman suffered minor injuries Tuesday during a battle between U.S. soldiers and suspected insurgents, the military said. He was standing next to an alleged insurgent who was killed during the shootout, the statement said.

The military said the cameraman was detained because there was probable cause to believe he posed "an imperative threat to coalition forces."

Officials are investigating the man's previous activities as well as "his alleged support of anti-Iraqi insurgency activities," the statement said.

Associated Press writer Mariam Fam in Baghdad contributed to this report.