Suspected militants riding on a motorcycle have opened fire on a vehicle carrying police officers in a former stronghold of the Pakistani Taliban, killing two of them and wounding two others.

Militants opened fire on a police vehicle and killed two officers on Thursday in restive northwest Pakistan before fleeing the scene, police said, a sign of increasing violence ahead of a summit of an Asian security grouping in the capital,

Pakistani police have clashed with supporters of a rights group for the Pashtun ethnic minority in the country's northwestern angered by a government ban imposed on the organization this week, leaving three people dead.