BAGHDAD -- An Iraqi soldier opened fire on a U.S. military team Saturday, killing two American soldiers and wounding three, the U.S. military said.
Iraqi officials described the attacker -- who was killed in the gunbattle -- as a soldier who also served as a Sunni Muslim preacher for his unit near Mosul, which is one of the last urban strongholds for Sunni insurgents.
Such an ambush could increase pressure on the Shiite-led government to try to root out possible turncoats and slow efforts to bring Sunni militiamen into the police and military as rewards for helping battle al-Qaida in Iraq and other insurgent factions.
But any possible slowdown of the Sunni outreach will meet resistance from Washington, which sees the sectarian reconciliation as essential for Iraq's stability and to keep security gains from rolling back.
A U.S. military statement said the attacker was killed after firing on the U.S. soldiers near the entrance to a combat outpost 12 miles south of Mosul.
A separate gunman fired at other U.S. soldiers at the outpost, then fled, according to Maj. Derrick Cheng, a spokesman for American forces in northern Iraq.
In the past, attackers have used military and police uniforms to bypass checkpoints and gain access to heavily guarded bases. But several Iraqi military officials said the gunman was a low-ranking Iraqi soldier.
The officials spoke on condition of anonymity because they were not authorized to speak to the media.
It was the latest case of a member of Iraq's security forces targeting U.S. troops. On Feb. 24, two Iraqi police officers in Mosul opened fire on a visiting U.S. military team, killing one American soldier and an interpreter. The gunmen remain fugitives.
Last week, a U.S. military spokesman, 1st Lt. John Brimley, called the February shooting "definitely an anomaly."
Saturday's attack follows the deadliest month for U.S. troops in Iraq since September -- with 18 American soldiers dying in Iraq in April.
Elsewhere, U.S.-backed Iraqi troops arrested the leader of a Sunni paramilitary group north of Baghdad in the town of Duluiyah.
Mullah Nadhim al-Jubouri, and his two brothers, Yassir and Thakir, were arrested on warrants accusing them of terrorism, the U.S. military said, without elaborating.
The move was likely to spark anger among members of the so-called Awakening Councils, which have turned against al-Qaida in Iraq in what is considered a key factor in the drop in violence.
The Iraqi government has assumed control of the groups from the U.S. military, but many of the Sunni guards accuse it of failing to pay them and of making unfair arrests.
In the northern city of Kirkuk, security patrols were boosted after an attempted suicide bombing Friday was foiled by guards at the last moment at a Shiite mosque.
Authorities identified the would-be attacker as a Syrian teenager who they believe was recruited by al-Qaida in Iraq. The suspect -- 19-year-old Ammar Afif Hamada -- was tackled on the doorsteps of the mosque while it was filled with worshippers.
The dramatic capture was welcome good news for Iraqi authorities after a spike in blasts by suspected Sunni insurgents that have claimed more than 200 lives since late April and raised question about the durability of recent security gains.
It also could offer investigators insights into insurgent operations in northern Iraq and smuggling routes from Syria -- long considered one of the main pipelines to replenish insurgent ranks from across the region.
Hamada traveled from Syria to the northern city of Mosul about a week ago, then arrived Wednesday in Kirkuk, where he was moved from safe house to safe house in mainly Sunni areas, according to a police officer involved in the investigation. The officer spoke on condition of anonymity because he wasn't authorized to release the information.
Kirkuk police chief Maj. Gen. Torhan Abdul-Rahman Youssef confirmed the details and said Hamada has been an al-Qaida operative in Iraq for the past four years and has confessed to participation in many operations in Diyala province and Baghdad.
Hamada, meanwhile, was being treated for serious head injuries at a hospital in Kirkuk after being beaten by guards and worshippers at the scene, police said.
Tensions have risen in Kirkuk as Kurdish leaders seek to incorporate it into their semiautonomous area, making it one of the most politically sensitive issues for Iraqi leaders and for U.S. military commanders preparing to withdraw their troops by the end of 2011.
The showdown is so volatile that Kirkuk was excluded from regional elections in January and the United Nations has offered a proposal for compromise plans.
U.S. Defense Secretary Robert Gates, speaking on CNN's "Fareed Zakaria GPS" in a segment to air Sunday, described Kirkuk's ethnic rifts as one of Iraq's most complicated puzzles.
"From an Arab-Kurd point of view, Kirkuk is a bigger problem by far than Mosul," he said. "Mosul is really still a security problem from the standpoint of al-Qaida is still using that as kind of their last redoubt, if you will. But, you know, I think (the Iraqis) will continue to work these things through."