BAGHDAD - Thousands of Shi'ite civilians charged with guarding neighborhoods in Iraq marched through Baghdad on Wednesday to demand an end to the sectarian violence that is ravaging the country.

Young men in uniforms and headbands, members of what are known as the popular committees, chanted as a speaker urged them to protect the neighborhoods from the Saddam Hussein loyalists leading a Sunni insurgency against the Shi'ite-led government.

"Stamp on terrorism," he said.

The crowd included members of the Badr Organization, one of the armed Shi'ite groups that Sunni Arabs accuse of running militia death squads, a charge they deny.

"We have to benefit from this wide popular base, and the state and Iraqi people should form these popular regional committees from the best of our young men to face terrorism," Abdul Aziz al-Hakim, one of Iraq's most powerful Shi'ite leaders, told the crowd.

"They will defend people of districts; Sunnis, Shi'ites, Arabs, Kurds and Turkmen. They do not differentiate between anybody."

Prime Minister Nuri al-Maliki, whose reconciliation plan has failed to reduce sectarian bloodshed, has promised to disband the militias many fear will push the country into civil war.

"The first enemy is the Baathist Saddam loyalists and their henchmen, the Islamic extremists," Hakim said.

Officially, the event was held to mark the third anniversary of the death of Hakim's brother, Ayatollah Mohammed Baqer al- Hakim, in a bombing in the southern city of Najaf.

But the speeches also covered explosive issues such as federalism, which is opposed by Sunnis who fear it will leave them deprived of oil in resource-poor central Iraq.

ROADSIDE BOMBS

"We believe that implementation of a federal system in Iraq will achieve justice and rebuild Iraq and guarantee the unity of the Iraqi people and land," Hakim said.

Two roadside bombs killed at least 12 people and wounded 13, mostly young soccer players, in the Baghdad district of Amel on Wednesday evening, a police source said. He said the bombs had been planted near a soccer field opposite a police station.

Two U.S. servicemen were killed in action in Anbar, the U.S. military said.

Earlier, three roadside bombs exploded in central Baghdad near a group of laborers seeking work, killing three people and wounding nine, police sources said.

In Madaen, south of Baghdad, 15 insurgents and three policeman were killed in fighting that began Monday night.

Gunmen in Baquba, north of Baghdad, killed the chief of the traffic police, Ahmed Abdel Hussein, and one of his bodyguards.

Two off-duty Iraqi soldiers and a civilian were killed when a roadside bomb exploded near a truck carrying wheat in Hawija, 70 km (45 miles) southwest of Kirkuk, police said.

A senior coalition officer said the leaders of almost a quarter of the 24,000-strong national police were suspected of crimes and sectarian violence and should be replaced.

"There are 26 battalions. Maybe five or six have leaders who have led them in a way that was either criminal, or sectarian, or both," the official, who spoke on condition of anonymity, told reporters at a briefing in Baghdad.

President George W. Bush has ordered more U.S. troops to Baghdad to quell sectarian bloodshed.

But many question the government's will to confront death squads that could be operating from within the security forces.

"There are (security) forces in Baghdad who don't feel that they have the got the backing of their government to confront the (militias) ... It puts the soldier on the street in a pretty tricky spot," the official said.

Bombings and shootings killed up to 61 people in Iraq on Tuesday, including at least 26 soldiers.

President Jalal Talabani said Iraqi forces could take over security at the end of the year and he was hopeful they could stamp out violence by then, ambitious goals in a country where 100 people are killed every day.

But he did not spell out what he meant. U.S. commanders say handing over security would involve several phases.