BAGHDAD - A suicide bomber attacked a mosque filled with Iraqi politicians and policemen Friday and another blew himself up inside the hospital where the wounded were taken, killing a total of 21 people in Saddam Hussein's hometown.

The twin attacks - as well as the fact that the bombers were able to infiltrate areas that were supposed to be secure - left people in Tikrit feeling under siege.

It was the third major attack in Tikrit this year, reflecting the difficulties Iraqi security forces face in protecting their own people from Sunni insurgents still intent on undermining the country's post-Hussein leaders, many of whom are Shiite.

Such violence is all the more troubling because of the approaching year-end deadline for American forces to leave.

The first bomber struck during midday Muslim prayers, blowing himself up inside a Sunni mosque packed with local officials and killing 16 people, including a police commander and a judge, officials said.

The mosque was inside a government-controlled compound where many officials live, and most in attendance were security or government employees.

Victims were taken to the main hospital in Tikrit, said the province's top medical official, Dr. Raeid Ibrahim. He said 54 people were wounded.

Hours later, a bomber walked into the hospital and blew himself up near the emergency room, where family of those wounded earlier had gathered, said Mohammad al-Asi, media adviser for the provincial governor.

Five people were killed and 16 injured, said an official at the hospital and a security official in Tikrit. They spoke on condition of anonymity because they were not authorized to speak to the media.

There was no claim of responsibility for either attack. Insurgents often target fellow Sunnis who work with the government because they perceive them as collaborators with Iraq's new, Shiite-dominated leadership.

Iraq's majority Shiites were persecuted under Hussein's Sunni-led regime.

Tikrit, 80 miles north of Baghdad, sheltered some of al-Qaeda in Iraq's most fervent supporters after the 2003 U.S.-led invasion ousted the dictator.