KABUL: Afghan authorities on Tuesday said “regional spy agencies” were behind a rare suicide attack targeting Shia Muslims that killed more than 80 people in a veiled reference to Pakistani intelligence.

Attorney General Eshaq Aloko said two men had been arrested over the December attack, which struck a crowd of worshippers on Ashura in Kabul.

President Hamid Karzai blamed Pakistani sectarian extremist outfit Lashkar-e-Jhangvi for the atrocity, which was unprecedented on such a holy day, and urged Islamabad to act.

Aloko said the attack was planned in Pakistan's northwestern city of Peshawar, by “regional spy agencies” aimed at “provoking sectarian violence”.

“Although the Jhangvi group claimed responsibility, it was masterminded by some spy agencies in our neighbouring countries,” Aloko said.

Afghans blame Pakistan for fuelling much of the violence in their country, where the Taliban are leading a 10-year insurgency against the government and 130,000 Western troops.

The prosecutor said one of those arrested came from Afghanistan's Nangarhar province, which borders Pakistan's militant-infested tribal belt, and was paid 10,000 Pakistani rupees ($100) to bring two suicide attackers to Kabul.

“One attacker blew himself up, the second fled the area,” Aloko said.

He said the two arrested men both confessed over the plot and the case was now closed.

The explosion happened at the entrance to a riverside shrine, where hundreds of Shias had gathered.

The Taliban denied responsibility for the attack, the deadliest in the Afghan capital in three years.

“The case is closed for us now. We have completed our investigation, and the case will be sent to the court,” Aloko said.