Pakistan has declared a state of emergency in the northwestern province of Khyber Pakhtunkhwa, effectively suspending the regional government run by the Pakistan Tehreek-e-Insaf party.

President Asif Ali Zardari announced on Sunday that he had approved recommendations made by the federal cabinet, which had convened earlier in the day under Prime Minister Shehbaz Sharif.

The emergency was invoked under two articles of the constitution dealing with security matters.

A statement from the prime minister's office said cabinet members had reviewed the situation and cited the "provincial government's deliberate disengagement from the fight against terrorism" as the basis for the move.

Khyber Pakhtunkhwa is governed by Pakistan Tehreek-e-Insaf, the party of jailed former Prime Minister Imran Khan. Khan has been imprisoned for more than three years but continues to command widespread popularity across the country.

The declaration comes as PTI had been preparing a march on the capital, Islamabad, to demand Khan's release.