Punjab's Home Minister Shuja Khanzada has been killed in a suicide attack in the Pakistani province, police say.

Twelve other people died in the attack at Khanzada's office in District Attock, about 80km (50 miles) north-west of the capital, Islamabad.

Khanzada was seen as the man in charge of the anti-terror campaign in Pakistan's biggest province.

A Sunni militant group with ties to al-Qaeda has said it ordered the attack.

Lashkar-e-Jhangvi said it was in response to last month's killing of its leader, Malik Ishaq.

Shuja Khanzada is the most senior Pakistani politician to have been killed by militants this year.

The impact of blast caused the roof of the building collapse and shattered windows in nearby houses. Photo: Dawn News

The minister's death is being seen as a significant blow to Pakistan's recent gains in the fight against militancy and extremism, says the BBC's Shahzeb Jillani in Islamabad.

Our correspondent says questions are being asked about his security as the home minister had reported threats made against him.

Khanzada was meeting supporters in his hometown of Attock when a large bomb exploded, causing the roof to cave in, trapping dozens under the rubble.

Leading tributes to the home minister, Prime Minister Nawaz Sharif said: "The courage and valour of Shuja Khanzada is message to the masterminds of terrorists that they are bound to be defeated."

Lashkar-e-Jhangvi has been behind some of the most violent attacks in recent years.

It was banned in Pakistan in 2001 and designated a terrorist group by the US in 2003. It has claimed the killings of hundreds of mainly Shia civilians in Pakistan.