A bomb smuggled into a village mosque Friday killed a prayer leader who also worked as a police officer in an area of northern Iraq considered the last stronghold of Sunni insurgents, an official said.

The explosives were hidden under a platform where Narjis Shiwash was overseeing prayers in Namrood, a mostly Sunni village about 18 miles south of Mosul. Three worshippers were injured, said the police official, who spoke on condition of anonymity because he was not authorized to speak to media.

The mosque was only lightly guarded and had none of the additional security cordons placed around many larger places of worship around Iraq during the height of sectarian bloodshed several years ago.

There were no immediate arrests, but suspicion fell on groups such as Al Qaeda in Iraq.

The Mosul area is considered the last major base for Sunni insurgents, who have targeted tribal leaders and others who assist security forces. On Sept. 25, at least 11 Iraqi soldiers were killed just outside Mosul, the nation's third-largest city.

In Baghdad, an American soldier was killed in a mortar attack at a sprawling base on the western edge of the Iraqi capital, the U.S. military said.

Insurgents have stepped up attacks against Iraqi security forces in recent months as U.S. troops have pulled back to bases outside Iraqi cities.

Insurgents have primarily targeted Iraqi forces and government officials but have also attacked U.S. troops across Iraq with mortar shells and roadside bombs.

The Multi-National Corps-Iraq soldier was killed Thursday in what is at least the second attack in two weeks at Camp Liberty, part of a group of American bases that make up the American headquarters in Iraq known as Camp Victory.

A rocket struck Camp Liberty last week but caused no casualties, said Army Lt. Col. David Patterson, a military spokesman.

The name of the soldier was being withheld pending notification of next of kin, the military said in a statement.

The death raised to at least 4,348 the number of U.S. military personnel who have died in the Iraq war since it began in March 2003, according to an Associated Press count.

The number of troops killed in combat has dropped dramatically since 2007 as violence has declined sharply, though there have been a number of U.S. soldiers who have died as a result of noncombat injuries.

With the decline in violence, the U.S. has accelerated its withdrawal from Iraq. Army Gen. Ray Odierno, the top commander in Iraq, has said 4,000 troops will be sent home in October ahead of schedule.

Under a U.S.-Iraqi security pact, the U.S. pulled out of Iraq's cities on June 30. President Barack Obama has ordered all combat troops out of the country by Aug. 31, 2010, leaving up to 50,000 troops in advising roles. All troops would withdraw from Iraq by the end of 2011, under the pact.

Iraqi casualties have also fallen off. September had the second-lowest death toll for Iraqis since The Associated Press began tracking casualties in May 2005. At least 238 people were killed, according to an AP count, based on reports from local police, military officials and hospitals. Only May 2009, with 225 deaths, was lower.

An Iraqi report, based on statistics from the defense, health and interior ministries, placed last month's Iraqi death toll at 203, including 125 civilians, 38 police officers and 40 soldiers.