US special envoy for reconciliation in Afghanistan, Zalmay Khalilzad, who negotiated a deal with the Taliban, has said an initial prisoner exchange between the armed group and the Afghan government was an "important step" towards peace.

According to the Red Cross, the Taliban released 20 Afghan security force prisoners on Sunday after the government released 300 "low-risk" Taliban captives, who have pledged not to return to the fight and are being let go based on various factors including their health, age and length of remaining sentence.

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"The release of prisoners is an important step in the peace process and the reduction of violence," Khalilzad said on Twitter on Monday.

(1/2) Welcome the release of prisoners by both the Afghan government and the Taliban. The release of prisoners is an important step in the peace process and the reduction of violence. — U.S. Special Representative Zalmay Khalilzad (@US4AfghanPeace) April 13, 2020

"Both sides should accelerate efforts to meet targets specified in the US-Taliban agreement as soon as possible," he added, noting the exchange was more important than ever with prison populations threatened by coronavirus outbreaks.

Khalilzad and the Taliban signed a deal on February 29 that paves the way for US and other foreign forces to quit Afghanistan in return for various commitments from the armed group.

The deal said the Afghan government would release 5,000 Taliban prisoners, while the armed group would free 1,000 Afghan security force personnel.

The exchange was supposed to have happened by March 10, allowing peace talks to begin between the Taliban and the Afghan government - but the process has been beset with problems.

Kabul has claimed the Taliban want 15 of their "top commanders" to be released, while the armed group have accused Afghan authorities of wasting time.

A small Taliban team met with the government to discuss a comprehensive prisoner swap last week, but walked out of talks after officials began releasing prisoners only gradually.

On Sunday, the Taliban told AFP news agency their decision to release a group of prisoners was "a goodwill step ... to accelerate the prisoner exchange process".