Iraqi officials say a suicide bomber has killed three people and wounded at least 10 others in central Baghdad.

Officials say the bomber targeted a police unit Wednesday in the Karradah neighborhood.

Also Wednesday, two Iraqi policemen were killed by a suicide bomber in the northern city, Mosul.

Violence in Iraq has dropped sharply over the past year, but the security situation remains fragile. 

The U.S. military has been transferring security responsibilities to the Iraqi government, with U.S. forces scheduled to withdraw from the country by 2011. 

Some information for this report was provided by AP.