Guard, right, walks inside mosque at the where shoe bomber blew himself up during Friday prayers

A suicide bomber has killed 10 people and wounded more than 20 others at a Shi'ite mosque in Baghdad, despite a massive security crackdown in the Iraqi capital.

Witnesses said the bomber detonated explosives in his shoes, as worshippers gathered for Friday prayers.  The mosque's imam blamed the attack on al-Qaida in Iraq.  A triple suicide bombing at the same mosque in April killed more than 80 people.

In a separate incident Friday, a mortar barrage slammed into a commercial area of northern Baghdad, killing two people and wounding 16 others.  

Tens of thousands of Iraqi and U.S.-led coalition troops are taking part in the security clampdown in Baghdad.  The operation began Wednesday.  U.S. Major General James Thurman says despite Friday's violence, the level of bloodshed in Baghdad has dropped in recent days.

General Thurman told Pentagon reporters via teleconference from Baghdad that the security operation is designed to disrupt terrorist cells and target groups opposed to the Iraqi government.  The general stressed that Iraqi forces are taking the lead in the crackdown.

Some information for this report was provided by AFP, AP and Reuters.