The Taliban have released a US engineer they had held hostage since 2020 in exchange for an Afghan tribal leader held in US custody since 2005.

Mark Frerichs was handed over at Kabul airport on Monday, the Taliban said.

In return they received Bashir Noorzai, a Taliban ally serving a life sentence for drug trafficking.

US President Joe Biden said that the swap required "difficult decisions" that he did not take lightly.

Mr Frerichs, 60, was abducted by the Taliban the year before the group swept back to power in Afghanistan and its Western-backed government collapsed.

He had been living and working in Kabul as a civil engineer for 10 years. Mr Frerich's sister, Charlene Cakora, said the family had never given up hope of getting him back.

"I am so happy to hear that my brother is safe and on his way home to us. Our family has prayed for this each day of the more than 31 months he has been a hostage," she said in a statement.

"There were some folks arguing against the deal that brought Mark home, but President Biden did what was right. He saved the life of an innocent American veteran."

Art Frerichs, Mr Frerichs' father, told the BBC that while they received a phone call from Mr Biden, they have yet to speak to Mark.

"We're definitely feeling very relieved. It's been a long time," he said.

The detention of the former navy officer has been a major impediment to improving relations between the US and the Taliban, whose government is still to be recognised by any country in the world.

President Biden said in January: "The Taliban must immediately release Mark before it can expect any consideration of its aspirations for legitimacy. This is not negotiable."

At least one other American remains in Taliban hands. Filmmaker Ivor Shearer and his Afghan producer, Faizullah Faizbakhsh, were detained in Kabul in August.

Eric Lebson, a former national security official who worked as a volunteer to help the Frerichs family, said he hoped Mr Biden's actions to secure Mr Frerichs' release "are an indicator of his commitment to do the same on an urgent basis for other Americans held hostage or wrongfully detained abroad".

"They are being held because they are Americans and they need the US government to bring them home," Mr Lebson said.

Bashir Noorzai was given a hero's welcome on his return to the Afghan capital, and was greeted by Taliban fighters carrying garlands of flowers.

"My release together with that of an American will make peace between the countries," he told a news conference.

Noorzai was a close ally and friend of Taliban founder Mullah Omar and helped finance the first Taliban government in the 1990s.

He did not hold an official position but "provided strong support including weapons", Taliban spokesman Zabihullah Mujahid told the AFP news agency.

Noorzai had served 17 years in US custody for heroin smuggling. Prosecutors said he ran a vast opium-growing operation in Kandahar province, the Taliban's traditional heartlands in the south of the country.

At the time of his arrest in 2005, he was considered one of the biggest drug dealers in the world, controlling more than half of Afghanistan's drug exports, which account for most of the world's harvest.

In 2008, he was convicted by a court in New York of conspiring to smuggle more than $50m of heroin into the United States.