A car bomb attack targeting a Pakistan police headquarters on Diesday killed at least 20 people including women and children and wounded more than 50 people in northwestern city Kohat.

Militants have launched a series of brazen assaults in the past week as Muslims mark the final days of the holy fasting month of Ramadan.

Six policemen were among the dead in the latest blast and police said the other victims were women and children who were breaking their fast in the garrison city, close to the lawless tribal areas of Khyber and Orakzai.

"It was a car bomb blast, we are investigating whether the car was parked or was exploded by a suicide bomber," Khalid Khan, a top administrative official in Kohat, told AFP

Provincial information minister Mian Iftikhar Hussain told AFP in the regional capital Peshawar: "At least 20 people have died and more than 50 were injured."

Fazal Naeem, a police spokesman in Kohat, confirmed the death toll.

A police residential complex was severely damaged and houses nearby had also collapsed in the sheer force of the explosion, trapping people in the rubble.

Frantic rescue workers were facing difficulties as electricitywas suspended after the blast.

There was no claim of responsibility, but the Pakistani Taliban has been blamed for similar bombings.

The Taliban said earlier Tuesday they would continue to target security forces after they claimed responsibility for a Monday attack in Lakki Marwat, in Khyber Pakhtunkhwa province, that killed 19 people including nine policemen.

"We are targeting Pakistani security forces because the government has allowed America to launch drone attacks on us," Tehreek-e-Taliban Pakistan (TTP) spokesman Azam Tariq told AFP by telephone.

"Rather it is on the Pakistan government's behest that drone attacks target us," he said.

"We will continue suicide attacks on security forces. Civilians should avoid proximity from them."

On Friday, the group vowed to carry out further attacks inside Pakistan and against the United States and Europe after the US State Department added it to a blacklist of foreign terrorist organisations.

The series of attacks come even as Pakistan struggles to deal with massive flooding that has killed nearly 1,800 people and left millions reliant on aid handouts.

On Friday, a suicide bomber killed at least 59 people at a Shia Muslim rally in Quetta, capital of the southwest province of Baluchistan.

That attack came just days after three suicide bombers killed 31 people and wounded hundreds more during a Shia mourning procession in Lahore. The attack was subsequently claimed by theTaliban.

Northwest Pakistan suffers from chronic insecurity, largely connected to the semi-autonomous tribal belt near Afghanistan, which Washington calls the most dangerous place on Earth and a global headquarters of al-Qaeda.

More than 3,700 people have been killed in the last three years in a series of suicide attacks and bomb explosions, many of them carried out by the Taliban and other Al-Qaeda-linked Islamist extremists.