Afghanistan's National Security Council, which is chaired by President Hamid Karzai, has accused "foreign intelligence services" of being behind the deadly attack on a Kabul restaurant, in a veiled reference to Pakistan.
Pakistan was the main supporter of the former Taliban regime in Afghanistan, and Afghan officials have long voiced suspicions about 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 released on Sunday from the palace said.
"Beyond the border" is a phrase commonly used by the Afghan government to refer to neighbouring Pakistan.
Taliban fighters claimed responsibility for Friday evening's suicide attack on a popular Lebanese restaurant in central Kabul in which 21 people, including 13 foreigners, were killed.
Among the dead were three Americans, two British citizens, two Canadians, the International Monetary Fund head of mission, and the Lebanese owner of the Taverna du Liban, which was a popular social venue for expats.
In the deadliest attack on foreign civilians since the Taliban were ousted in 2001, one attacker detonated his suicide vest at the fortified entrance to the restaurant before two other fighters stormed inside and gunned down diners and staff.
The accusation of Pakistani involvement is likely to damage regional peace efforts as Pakistan, which has been battling the Pakistani Taliban, is seen as crucial to encouraging the Afghan Taliban to open talks.
Many Afghan Taliban leaders seek shelter in Pakistan, and Islamabad's Inter-Services Intelligence (ISI) spy agency is often accused of maintaining ties to the fighters to ensure future influence in Afghanistan after US-led NATO troops withdraw.
Pakistani officials were not immediately available to comment on the accusations from Kabul, but Islamabad has always denied any links with the Taliban.
Karzai earlier condemned the restaurant attack and called on NATO forces "to target terrorism" in his country.
Social activists and local residents held a small demonstration in Kabul on Sunday, laying flowers and placards outside the restaurant demanding peace.
Daffodils and roses were laid next to placards, some written in English reading "Peace is what we want" and "We will win, terrorism will lose", outside the entrance to the Lebanese restaurant.
Afghan officials vowed to investigate how the suicide attackers penetrated one of the most secure parts of Kabul.
Three police chiefs responsible for the Wazir Akbar Khan district have been suspended over the security breach.
United Nations chief Ban Ki-moon paid tribute to the four UN staff killed in the attack, and pledged that the UN would maintain its work in Afghanistan.
The blast has led to embassies, aid organisations and international institutions re-assessing whether their staff can operate safely in the Afghan capital.
NATO combat forces are withdrawing from Afghanistan this year after more than a decade of fighting the Taliban, but negotiations have stalled over a deal to allow some US and NATO troops to stay after 2014.
Underlining Pakistan's own battle with rebel fighters, Pakistan army helicopters fired missiles killing three fighters in the northwest of country on Sunday after a bomb killed 22 soldiers in the same region earlier in the day.