Afghan authorities say militants have attacked a police checkpoint in southern Afghanistan, killing three policemen and wounding six others.

Kandahar province spokesman Javid Faisal says militants attacked the checkpoint in Kandahar city around 6 am Tuesday.

A gunbattle between the police and insurgents lasted for an hour.

On Monday in Kandahar province, three gunmen wearing Afghan police uniforms killed a Nato service member.

Nato did not disclose the location of the incident, but Salim Ahsas, an Afghan police chief for the southern region, says it occurred in Zhari district.

Monday’s attack is among nearly 20 this year that have raised the level of mistrust between the coalition and their Afghan partners as Nato works to hand over security to local forces. (AP)