Suspected militants killed four policeman in an ambush near Pakistan's northwestern city of Peshawar today, police said.
The militants armed with Kalashnikov assault rifles opened fire on a police van and then threw an explosive, setting the vehicle alight, in an attack about 10km south of Peshawar, the capital of North West Frontier Province.
Police said it may have been a revenge attack, after police killed a militant during a clash last week in the nearby town of Nowshera.
Separately, four children were killed in an explosion in the northern town of Chitral late on Sunday.
Pakistan has seen a wave of militant violence, most of it in the country's northwest and the adjoining lawless tribal belt on the Afghan border and hundreds of people have been killed since the middle of the last year.
The violence had subsided after Pakistan's new government to came to power after defeating allies of President Pervez Musharraf in an election in February, and began peace negotiations with militants.
Although similar pacts the past have failed to curb militancy, the government hopes the tribal leaders can use their influence to rein in militants and stop violence in Pakistan and cross-border infiltration into Afghanistan.