KABUL: Prospects of peace in Afghanistan after 19 long years of war brightened on Friday when Kabul started releasing 400 Taliban prisoners who were described by President Ashraf Ghani as a "danger to the world" on Friday. 

The Afghan government and the Taliban are set to meet within days of the prisoner release being completed, in a move that has drawn widespread condemnation after it emerged many of the inmates were involved in attacks that killed scores of Afghans and foreigners.

A group of 80 prisoners was released on Thursday, said National Security Council spokesman Javid Faisal, tweeting that it would "speed up efforts for direct talks and a lasting, nationwide ceasefire".

The peace talks will be held in Doha, Qatar.

The release of the 400 militants was approved at the weekend by a gathering of thousands of prominent Afghans called by Ghani after the authorities initially refused to free the militants.

The prisoners include some 44 insurgents of particular concern to the United States and other countries for their role in high-profile attacks, according to an official list seen by AFP.

Australian Prime Minister Scott Morrison said earlier this week he had lobbied for a former Afghan army soldier, who went rogue and killed three Australian colleagues, to stay in jail.

Ghani warned on Thursday that the hardened criminals were "likely to pose a danger both to us and to (America) and to the world".

"Until this issue, there was a consensus on the desirability of peace but not on the cost of it," Ghani said in a video conference organised by a US think tank.

"We have now paid the major instalment on cost and that means peace will have consequences," he added, noting that the release of "hardened criminals" and drug dealers was "likely to pose a danger both to us and to (America) and to the world".

A prisoner swap formed part of a deal signed by the Taliban and the United States in February, which saw Washington agree to withdraw its troops from Afghanistan in return for a pledge from the insurgents to hold peace talks with the Afghan government.

The Afghan government was excluded from that deal.

The February deal had stipulated that Kabul release 5,000 militants in return for 1,000 Afghan government prisoners held by the insurgents.

While Kabul released the bulk of Taliban prisoners as agreed in the deal, it had baulked at freeing the final 400.

The "loya jirga" -- the traditional gathering of tribal elders and other prominent citizens called by Ghani at the weekend -- approved the release to pave the way for talks and a possible ceasefire.

They asked authorities to monitor the freed prisoners to ensure they did not return to the battlefield.

Ahead of the jirga, US Secretary of State Mike Pompeo had urged the gathering to release the prisoners, although he acknowledged the move was "unpopular".

The Taliban, meanwhile, has warned of possible attacks against the freed prisoners by extremists of the Daesh group in coordination with Afghanistan's spy agency.