A U.S. aid organization says one of its American workers in Iraq and three other people were killed in an ambush Wednesday in Baghdad.

An official in Washington with the National Democratic Institute, Leslie Campbell, says the American and three security personnel, including an Iraqi, a Croatian and a Hungarian, were killed in the attack.

He said it is not clear who carried out the attack.

The National Democratic Institute is a non-profit organization that is providing training and advice to Iraqi political parties, civil groups and parliamentarians.

Campbell says the group has no immediate plans to end its mission in Iraq, but he says the situation will be re-assessed in light of the attack.

Some information for this report was provided by AFP.