The three Americans killed by the roadside bomb were members of the 89th Military Police Brigade. The Associated Press reported that a soldier assigned to the Third Brigade Combat Team, First Cavalry Division, died Saturday in an explosion in Diyala, east of the Iraqi capital.  Elsewhere, snipers attacked a joint American and Iraqi patrol in Baquba. The resulting exchange of gunfire left at least five people dead, officials said, though none were believed to be Americans.  In the southern part of the country, skirmishes between Iraqi security forces and militia members in Samawa intensified.  Militia fighters linked to the militant cleric Moktada al-Sadr fired rocket-propelled grenades at police headquarters and state buildings as the central government in Baghdad struggled to end the confrontation.  Mr. Bolani, during his news conference, sought to play down the three days of clashes in Samawa, which is about 230 miles southeast of Baghdad  He said he believed that the government’s forces “can face these outlaw groups.”  He refused to identify the groups, but the police said they were members of the Mahdi Army militia, which is controlled by Mr. Sadr.  Local officials expressed fears that the clashes would expand to include Nasiriya Province, which is only 46 miles from Samawa. In nearby Diwaniya, police officials said, the local security forces were on a heightened state of alert.  Elsewhere, the Iraqi security forces continued to come under attack as a suicide bomber killed seven police officers in Miqdadiya, 50 miles northeast of Baghdad, a police official said.  A version of this article appears in print on , on Page A15 of the New York edition with the headline: Baghdad Roadside Bomb Kills 3 U.S. Soldiers. Order Reprints| Today's Paper|Subscribe
Officials also said seven Iraqi police officers died when a suicide bomber attacked a police station in the city.