Insurgents seeking to disrupt Iraq's national elections later this month have killed another election official, bringing to at least seven the number of election workers killed in recent weeks.

Police say the election supervisor was shot as he left a Baghdad polling station Thursday.

Also Thursday, three officials from a leading Kurdish political party were killed in an ambush in Mosul, and a U.S. soldier was killed and three were wounded in a roadside bomb blast.

Earlier Friday, a minibus full of civilians collided with a U.S. tank north of Baghdad, killing six Iraqis and injuring eight.

And in a separate development, Iraqi and U.S. officials say 28 prisoners from the Abu Ghraib prison near Baghdad escaped Thursday night while being transported to another facility. None of them are suspected insurgents.