An Afghan official says four Afghan policemen have been killed accidentally by U.S. troops in southern Kandahar province.

Kandahar governor Asadullah Khalid said a misunderstanding led to the clash in Maiwand district late Monday. He said the police fired into the air and the U.S. soldiers mistook them for Taleban insurgents.

The U.S. military in Kabul said it had no information about the incident.

Several Afghan policemen also were killed earlier this month when U.S. troops mistook them for militants and fired at their vehicle in Helmand province.

In a separate incident in Kandahar province, a roadside bomb tore through a vehicle of a private U.S. security firm early Tuesday, wounding at least three Afghan employees.

Some information for this report provided by AFP and Reuters.