Iraqi police say at least 19 people were killed and many others wounded when several Shi'ite mosques were bombed in Baghdad on Friday.
One deadly blast occurred in Baghdad's northern Shaab district.
The attacks happened as people were leaving Friday prayers.
Violence in Iraq has dropped sharply during the past year, but attacks increased in the weeks leading up to and following the June 30 withdrawal of U.S. combat troops from Iraqi cities.
On Thursday, two bomb attacks killed at least 13 people, including a blast targeting a Sunni political party in Baquba.
Police say eight people were killed and 10 wounded in an explosion inside the headquarters of the Reform and Development Party in Diyala province, north of Baghdad, around the time some party members were holding a meeting.
In western Iraq, police say a suicide bomber blew up his vehicle, killing at least five people and wounding 15 others. Authorities say the attack happened close to a police station in al-Qaim near the Iraq-Syria border.