Taliban militants freed Pakistan's envoy to Afghanistan on Saturday, following the release of more than 40 of their own men by Pakistani authorities over the past few days, according to a senior security official.

Ambassador Tariq Azizuddin was released in South Waziristan, where he was being held by fighters loyal to Baitullah Mehsud, the leader of the Pakistani Taliban, the official said.

The government has yet to give an official account of the circumstances surrounding the envoy's release.

"I can confirm he is released, and he is safe and sound," Foreign Ministry spokesman Mohammed Sadiq said.

Azizuddin, 56, went missing on February 11 along with his driver and a guard as he was travelling from the north-western city of Peshawar to the Afghan-Pakistani border. He was on his way back to the Afghan capital, where he had been ambassador since 2005.

Over the past few days more than 40 Taliban fighters held captive by the authorities had been released, though it is uncertain whether the ambassador was exchanged for an specific militant, according to a senior security officer.

The officer, speaking on condition of anonymity, said the envoy was originally abducted by one of several kidnap gangs operating in and around the historic Khyber Pass, linking landlocked Afghanistan with Pakistan's northwest.

But he was subsequently passed on to the Pakistani Taliban, who moved him to South Waziristan, at the southeast end of the tribal belt, where he was held in the Mehsud tribal lands by men loyal to Baitullah Mehsud.

Pakistan's new government, sworn in at the end of March, has begun a policy of engagement, negotiating through tribal leaders to persuade Mehsud to halt militant operations from the region.

The ambassador represented one of Mehsud's main bargaining chips and was the last remaining high value captive the Taliban held.

HOME SOON

A relative said Azizuddin was expected to return home to his family shortly.

"The authorities contacted us and said that Aziz has been released and he would be back by the evening," a family member told Reuters.

The security official said he believed the ambassador's driver and guard had also been released.

Mehsud's notoriety spread after the Pakistan government and America's CIA made him prime suspect in the assassination last December of former prime minister Benazir Bhutto.

Mehsud has denied any role in her killing, and the new government, led by Bhutto's party, wants a U.N. investigation as it doesn't trust the previous government's findings.

Last month, Azizuddin appeared in a video on an Arabic television saying he was being held by the Taliban and urged the Pakistani government to meet their demands.

The bespectacled and grey-bearded ambassador also complained of high blood pressure and chest pains in the video, which showed two of his captors wearing baggy trousers and tunic, common to the frontier region, and brandishing assault rifles.

The long tribal belt on the border is notorious for being a haven for smugglers and bandits and turned into a major sanctuary for al Qaeda and the Taliban militants who fled from Afghanistan after a U.S.-led invasion in the wake of the September 11 attacks in 2001.

Scores of people have been abducted in the dangerous border region and the ambassador's disappearance highlighted mounting lawlessness in the tribal areas.

The security situation in Pakistan has deteriorated markedly since mid-2007, mainly in the northwest, with militants linked to the Taliban and al Qaeda carrying out suicide bombings.

More than 600 people have been killed in militant related violence since the beginning of this year, but since the peace talks began the violence has tapered off.