A suicide bomber has killed 10 people and wounded 11 others when he blew himself up after evening prayers in a mosque in Fallujah, west of Baghdad.
Police said the bomber had entered the office of the mosque where the imam, his son and a group of worshippers had been meeting.
The United States is pushing for a political accord between Iraqi leaders to reduce sectarian violence that has killed tens of thousands of Iraqis.
In the city of Kerbala, police have killed three people in clashes with pilgrims where thousands of Shia have gathered.
Police said they opened fire on a large crowd of pilgrims infuriated by the strict security measures in force in the city for the celebrations, killing three and wounding 13. The shots were fired after the pilgrims began brawling with the policemen.
Earlier, President George W Bush has praised a new political accord reached by Iraqi leaders, but said more needed to be done.
As the 15 September deadline for a key report on the war strategy approaches, Mr Bush sought to assure Iraqi leaders that the United States would not waver in its support.
He earlier called Iraqi Prime Minister Nuri al-Maliki and other leaders to congratulate them on reaching the agreement.
The accord was announced late on Sunday between Iraq's main Sunni Arab, Shia and Kurdish leaders on measures to readmit former members of Saddam Hussein's Baath Party to public life and release many detainees.
But the Sunni Arab vice president who signed the agreement said it would not be enough to reverse a decision by the disaffected Sunni Arab minority to quit the cabinet.
Mr Bush's comments come in the face of waning public support for the war and after some top Democrats called for Mr Maliki's ouster.
