A suicide bomber has rammed an explosives-laden vehicle into a hospital, killing 11 people in north-west Pakistan, say police.

Nearly 20 people were injured by the blast in the Shia Muslim-dominated Hangu district, Khyber Pakhtunkhwa province, according to police.

Investigators said the explosion was a sectarian attack.

It comes after the start of the Islamic holy month of Muharram, which is especially important for Shias.

"A car rammed into the hospital while people were praying in a hall and we have reports of at least 11 killed," the Reuters news agency quoted Hangu police chief Abdul Rashid as saying.

A tractor and trailer carrying 250kg (550lb) of explosives were used for the attack, Hangu police spokesman Fazal Naeem told news agency AFP.

It was the fourth major suicide attack this week in Pakistan.

On Monday, two bombers killed more than 40 people as they attacked anti-Taliban militia talks in Mohmand, in the north-western tribal belt.

On Tuesday, a suicide attacker failed in an attempt to assassinate the chief minister of Pakistan's south-western province of Balochistan.

On Wednesday, a bomber blew himself up near a minibus in the town of Kohat, not far from Hangu, killing at least 16 people.

Source : bbc.co.uk