Afghanistan's National Security Council, which is chaired by President Hamid Karzai, on Sunday accused "foreign intelligence services" of being behind the deadly attack on a Kabul restaurant, in an apparent reference to Pakistan.
Pakistan was the main supporter of the former Taliban regime, and Afghan officials have long voiced suspicions about the connections between the hardline movement and Islamabad's powerful intelligence services.
"The NSC said such sophisticated and complex attacks are not the work of the ordinary Taliban, and said without doubt foreign intelligence services beyond the border are behind such bloody attacks," a statement from the palace said.
The Taliban claimed responsibility for Friday evening's suicide assault on a popular Lebanese restaurant in central Kabul in which 21 people, including 13 foreigners, were killed.
Desperate customers tried to hide under tables as one attacker detonated his suicide vest at the fortified entrance to the Taverna du Liban and two other militants stormed inside and opened fire.
Among the dead were three Americans, two British citizens, two Canadians, the International Monetary Fund head of mission, and the restaurant's Lebanese owner.
A female Danish member of the European police mission in Afghanistan and a Russian UN political officer also died in the massacre, which was the deadliest attack on foreign civilians since the Taliban were ousted in 2001.
The accusation by the Afghan government is likely to damage regional peace efforts as Pakistan, which is also battling a homegrown Islamist insurgency, is seen as crucial to encouraging the Afghan Taliban to open talks.
Many Taliban leaders seek shelter in Pakistan, and Islamabad's Inter Services Intelligence (ISI) spy agency is often accused of maintaining ties to the militants to ensure future influence in Afghanistan after US-led NATO troops withdraw.
President Karzai on Saturday condemned the restaurant attack, and called on NATO forces "to target terrorism" in the country.
Afghan officials have vowed to investigate how the three suicide attackers penetrated one of the most secure districts of Kabul.
Three police chiefs responsible for the Wazir Akbar Khan district have been suspended over the security breach.
"The police officers will be questioned to see how this attack happened," interior ministry spokesman Sediq Sediqqi told AFP at a rally on Sunday of about 100 protesters outside the targeted restaurant.
"We are going to be very serious to make sure that these shortfalls will not happen in the future," he said.
A series of checkpoints known as the "ring of steel" was established in 2009 after repeated attacks in the city centre, but the militants evaded armed police tasked with searching people and vehicles.
Demonstrators holding signs reading "We denounce terrorism" gathered at the scene of the attack to protest at the Taliban insurgency against the US-backed Kabul government.