A Pakistani government team mediated a seven-day ceasefire deal between rival sectarian groups on Sunday, halting days of clashes that have killed some 70 people and injured dozens in the northwest of the country.

The violence began when gunmen attacked convoys of civilian vehicles on Thursday, killing at least 40 people, mostly Shi'ite Muslims.

That sparked retaliatory attacks against Sunni Muslim residents and there were pitched battles between armed groups from both sides.

Armed Shi'ite and Sunni Muslims have engaged in tribal and sectarian rivalry for decades over a land dispute in Kurram district near the Afghanistan border.

"Both sides have agreed to a week-long ceasefire which is expected to be extended," Muhammad Ali Saif, a member of the mediation team, told Reuters by phone, adding that major clashes had already stopped.

Saif, who is the information minister of Khyber Pakhtunkhwa province - where Kurram is located - said both sides also agreed to exchange prisoners, including women and the bodies of those killed in the clashes.

The prisoners and bodies would be exchanged with assistance from Pakistani paramilitary forces.

The team flew into Parachinar, Kurram's main city, on Saturday and met Shi'ite and Sunni tribal leaders with the entire district under curfew and armed groups roaming the streets.

Saif said news of the ceasefire should also halt smaller skirmishes that had been reported in remote areas of the district.

Another member of the mediation team, Akhtar Hayat Gandapur, the police chief of Khyber Pakhtunkhwa, said Shi'ite leaders were demanding the immediate arrest of those involved in attacking passenger vehicles, as well as compensation for the victims and safety assurances for travelers.

The government is yet to identify or publicly name who the attackers were and no one has claimed responsibility. (Reuters)