Ten Afghan civilians were killed Thursday in a NATO airstrike on three vehicles carrying election campaign workers in northern Afghanistan, President Hamid Karzai said in a statement.

Karzai strongly condemned the incident, in a statement confirming earlier reports of an airstrike in which election workers were killed in Takhar province.

"In the war on terror, pro-democracy people should be distinguished from those who fight against democracy," the statement quoted him as saying.