U.S. Army Spc. Dan Seitz, 22, from Pensacola, Fla., is seen at a newly established outpost for Delta Company, 4th Battalion, 31st Infantry Regiment, 2nd Brigade, 10th Mountain Division, on Saturday in Quarghuli village, near Youssifiyah, Iraq. A May 12 attack in Quarghuli left four U.S. soldiers and an Iraqi soldier dead and three comrades missing.

Baghdad ? U.S. forces broadened their hunt Saturday for three missing comrades beyond the rural area south of Baghdad where they disappeared, and their top commander expressed optimism that at least two of them were still alive a week after their isolated outpost was ambushed.

At least one soldier was killed Saturday and four others wounded as insurgents attacked the searchers with guns, mortars and bombs. The military reported a dozen other U.S. troop deaths in Iraq since Thursday.

Northeast of the capital, there was more gruesome Iraqi-on-Iraqi murder. Men in Iraqi army uniforms rousted Kurdish villagers from their homes, separated out the able-bodied men, and shot dead 15, according to an Iraqi general and a Kurdish political party.

It was the latest incident in months of sectarian killings in lawless Diyala province, and officials said Saturday that the local army commander was fired by the government.

The search for the missing soldiers involves some 4,000 troops who “will not stop searching until we find our soldiers,” said Lt. Col. Christopher Garver, a U.S. military spokesman in Baghdad. “We’re using all available assets and continuing to assault the al-Qaida in Iraq network,” he said.

Acting on a tip, Garver said troops raided a building in Amiriyah on Saturday morning and captured nine Iraqis suspected of involvement in the attack. Amiriyah is a stronghold of Sunni insurgents with close tribal ties to Quarghuli, where the outpost was overrun.

He said U.S. troops also detained two Iraqis in Baqouba who he said were “associated” with the al-Qaida command network. He did not tie those arrests directly to the missing soldiers. Their outpost in Quarghuli is about 12 miles south of Baghdad and about 50 miles from Baqouba, a violence-wracked city to the north.

A group that claims ties to al-Qaida has claimed responsibility for the May 12 attack that resulted in the kidnapping and the deaths of four American soldiers and an Iraqi aide. However, there has been no evidence, such as photos, video or audio, released by that or other groups.