BAGHDAD – A military panel today sentenced an Army sniper to five months in prison, a reduction in rank and forfeiture of pay for planting evidence in connection with the deaths of two Iraqi civilians.

The country’s sectarian violence, meanwhile, claimed 18 more lives today, including six people killed when a suicide truck bomber detonated his explosive payload near a Humvee filled with Iraqi soldiers, officials said. Two American soldiers also were killed — one hit by “enemy gunfire” in Diyala province and the other fatally shot during a firefight in Baghdad, the American military said.

Specialist Jorge G. Sandoval, 22, was acquitted of murder charges in the April and May deaths of two unidentified men. The panel decided he was guilty of a lesser charges of placing detonation wire on one of the bodies to make it look as if the man was an insurgent.

“I feel fortunate that I have been served this sentence,” Sandoval said. “I’m grateful that I’m able to continue to be in the Army.”

The prosecution had argued Sandoval should be sentenced to five years in prison.

Sandoval, of Laredo, Texas, had faced five charges in the deaths of the two unidentified Iraqi men. In dramatic testimony during the two-day court-martial, Sandoval’s colleagues testified they were following orders when they shot the men during two separate incidents near Iskandariyah, a volatile Sunni-dominated area 30 miles south of Baghdad, on April 27 and May 11.

Sergeant Evan Vela and Staff Sergeant Michael Hensley will be tried separately in the case. All three soldiers are part of the Headquarters and Headquarters Company, 1st Battalion, 501st Infantry Regiment, 4th Brigade (Airborne), 25th Infantry Division, based at Fort Richardson, Alaska.

Gary Myers, one of Sergeant Vela’s lawyers, claimed this week that Army snipers hunting insurgents in Iraq were under orders to “bait” their targets with suspicious materials, such as detonation cords, then kill those who picked up the items. He said his client was acting on orders.

Asked about the existence of the “baiting program,” Captain Craig Drummond, Sandoval’s military defense attorney, said it was unclear “what programs were going on out there and when,” especially “if there were things that were done that made the rules of engagement not clear.”

Today, Iraqi soldiers acting on a tip tried to intercept the suicide driver as his pickup truck headed toward Mosul, 225 miles northwest of Baghdad. As the Iraqi Humvee neared the truck, the driver detonated his explosive payload, according to the officer who spoke on the condition of anonymity for fear of reprisal. Three soldiers and three civilians were killed, the official said.

Late yesterday, police officials said Iraqi Interior Ministry commandos handed over nine decomposing bodies to a hospital in Samarra, 60 miles north of Baghdad. The officials requested anonymity because they were not authorized to release the information.

Earlier yesterday, Iraq’s prime minister told The Associated Press that a Senate proposal seen in Iraq as an attempt to split the country into regions according to religious or ethnic divisions would be a “catastrophe.”

The nonbinding Senate resolution calls for Iraq to be divided into federal regions under control of Kurds, Shiites and Sunnis in a power-sharing agreement similar to the one that ended the 1990s war in Bosnia. Senator Biden, Democrat of Delaware, was a prime sponsor of the measure.

The Kurds in three northern Iraqi provinces are running a virtually independent country within Iraq, while nominally maintaining relations with Baghdad.

They support a formal division, but both Sunni and Shiite Muslims have denounced the proposal.

The majority Shiites, who would retain control of major oil revenues under a division of the country, oppose the measure because it would diminish the territorial integrity of Iraq, which they now control. Sunnis would control an area with few if any oil resources. Kurds have major oil reserves in their territory.

“It is an Iraqi affair dealing with Iraqis,” Prime Minister al-Maliki told AP yesterday on a return flight to Baghdad from New York, where he appeared at the

U.N. General Assembly. “Iraqis are eager for Iraq’s unity. … Dividing Iraq is a problem, and a decision like that would be a catastrophe.”

Iraq’s constitution lays down a federal system, allowing Shiites in the south, Kurds in the north and Sunnis in the center and west of the country to set up regions with considerable autonomous powers.

Nevertheless, ethnic and sectarian turmoil have snarled hopes of negotiating such measures, especially given deep divisions on sharing the country’s vast oil resources. Oil reserves and existing fields would fall mainly into the hands of Kurds and Shiites if such a division were to occur.