An official says four Afghan policemen have been killed in a volatile area in southern Afghanistan, AP reported.

Helmand province spokesman Daoud Ahmadi says the predawn attack occurred Tuesday at a checkpoint near the Information and Cultural Affairs Ministry's directorate in the provincial capital of Lashkar Gah.

Ahmadi says it's not clear who killed the officers and that an investigation is under way.

Taliban militants frequently target Afghan security forces and officials to undermine the U.S.-backed government.