The prominent Pakistani cleric Maulana Samiul Haq, known as the “father of the Taliban”, has been killed in a knife attack at his home in Rawalpindi.

Haq’s son, Hamidul Haq, said his father was alone in his bedroom when he was attacked by an assailant, who escaped undetected.

“My father has been martyred. He was alone at his home. His guard had gone out minutes before the attack and upon his return, he saw my father in critical condition,” he told reporters.

Police said Haq, 81, was taken to a nearby hospital, where he died.

Yousaf Shah, Haq’s spokesman, said neither the attacker nor their motive was yet known.

Soon after his death, scores of Haq’s supporters rioted, damaging shops and vehicles in Islamabad and Rawalpindi. Haq’s family appealed to his followers to remain peaceful.

Haq, a well-known religious scholar with a large following among radical Islamists, was the head of his faction of the Jamiat Ulema-e-Islam (JUI) party.

His Haqqani seminary taught many of Afghanistan’s Taliban and thousands of other students a strict interpretation of Islam.

Sirajuddin Haqqani, the leader of the Haqqani network, a US-designated terrorist organisation, was one of dozens of Taliban leaders who graduated from Haq’s seminary, located in the conservative Khyber Pakhtunkhwa province on the border with Afghanistan.

In recent weeks, dozens of Afghan clerics appealed to Haq to use his influence with Afghanistan’s Taliban to plot a path to peace that would end the 17-year war there.

Pakistan’s president, Arif Alvi, and the prime minister, Imran Khan, condemned Haq’s killing.

“We lost a great scholar and religious leader today,” said Khan in a statement from China, where he is on an official visit.

Khan was widely criticised for embracing Haq ahead of the elections in July that brought the cricketer-turned-politician to power.

The provincial government in Khyber Pakhtunkhwa donated millions of dollars to Haq’s hardline seminary. Khan defended the move, saying he wanted to see Pakistan’s thousands of religious schools broaden their curriculum.

Haq’s funeral is expected to be held on Saturday in Akora Khattak.