Two soldiers were killed in that attack, the officials said. Two more soldiers were killed by snipers on Saturday morning, they said.

That was followed Saturday by the abduction of four soldiers from near a military base near Falluja, the officials said. The four, who were in civilian clothing, were on their way home for a short vacation when they were kidnapped, they said.

Al-Maliki on Friday said the violence in Falluja doesn't surprise his administration. He cited "conspiracies" plotted by regional intelligence services, vestiges of the old regime, al Qaeda and those with sectarian agendas.

The government, he said, has warned before about "those who have hostile agendas against Iraq, its political process and its democracy." He said dangers are "increasing day after day in an attempt to blow up the security situation in the country and drag the armed forces into confrontations."

The protest in Falluja was the latest in a series held in predominantly Sunni regions of Iraq. They have been countered by mostly Shiite, pro-government demonstrations, raising fears that the sectarian division could bring violence in the streets.

The protests have grown in recent weeks. They began in late December when Sunni demonstrators took to the streets in Anbar province, which borders Jordan and Syria, to protest al-Maliki's order to arrest the bodyguards of Finance Minister Rafaie al-Esawi, a Sunni.

The arrest of al-Esawi's bodyguards came just hours after President Jalal Talabani, a Kurd who is widely viewed as a stabilizing political force in Iraq, left the country about two weeks after suffering a stroke.

The protesters also are demanding the release of detainees they said are held without charges, calling the government corrupt and accusing it of unfairly targeting Iraq's Sunni people.

Iraq's Arab Sunnis and Kurds have accused al-Maliki and his Shiite political party of working to consolidate power in Iraq by cutting them out of the political process, an allegation that comes as U.S. lawmakers raise concerns about Iraq strengthening its ties with Shiite-dominated Iran.

Sunnis make up about 20% of Iraq's estimated population of more than 27 million, whereas about 60% to 65% are Shiite.

Since the fall of Saddam Hussein's Sunni-dominated regime in 2003, Sunnis in Iraq have been largely disaffected. The gulf was widened in 2005 when Sunnis boycotted the country's election, opening the way to a heavily dominated Shiite government.

The sectarian divisions translated into violence in the streets in 2006 and 2007, with fighting that nearly ripped the country apart.