At least 17 policemen were killed and three others injured after militants ambushed a police convoy in Afghanistan's Helmand province, sources said on Saturday.

The ambush took place late Friday night in Konjak area of Musa Qala district after militants attacked the convoy from neighbouring Baghran district, a district security source told Xinhua news agency.

About 10 armed militants were killed and seven others injured during the clash, the source added.

Three police vehicles were destroyed and two vehicles were seized along with police weapons by fleeing militants following the clash, the source added.