A British journalist held captive by extremists in Pakistan's militant-hit northwest has been released, the British embassy confirmed Thursday.

Journalist Asad Qureshi went missing in March while travelling to North Waziristan -- a hotbed of Islamist militancy -- with a retired army officer and a prominent Pakistani ex-spy who was killed by their captors.

"We can confirm Asad Qureshi has been released and our consular team are providing him with consular assistance," said George Sherriff, a spokesman for the British High Commission in Islamabad, giving no further details.

The fate of the third captive, retired military officer Sultan Ameer Tarar, known as "Colonel Imam", could not be confirmed.

Qureshi, a documentary film producer of Pakistani origin, lived in Britain but spent the last few years in Pakistan -- first working in the information ministry during the government of former military ruler Pervez Musharraf.

He later returned to documentary work and was believed to have been working on a film about the Taliban at the time of his capture.

A previously unknown group calling themselves Asian Tigers earlier claimed to have kidnapped the men and sent a video of one of their captives, former spy Khalid Khawaja, to the media, before apparently killing him.

An email purportedly sent by the faction said they killed Khawaja because the government did not accept the conditions they had set for his release.

Khawaja, a former Inter-Services Intelligence (ISI) officer and reported associate of Osama bin Laden, was found dead in April with a note accusing him of spying for the United States, according to security officials.

His body was dumped in Mir Ali town in North Waziristan, part of Pakistan's tribal belt bordering Afghanistan.

Khawaja headed a local human rights group and campaigned on behalf of missing people allegedly detained by Pakistan's intelligence agencies in the fight against Islamist militants.

Under Musharraf, Khawaja was arrested several times and once charged with possession of banned literature, propagating militancy and inciting hatred against the government.

Khawaja reportedly met Bin Laden in Afghanistan and reputedly claimed close ties to the Al-Qaeda mastermind, the United States' most wanted man.

Washington has branded the rugged tribal area on the Afghan border a global headquarters of Al-Qaeda and the most dangerous place on Earth.

Taliban and Al-Qaeda-linked commanders living in the tribal belt are the target of an ongoing drone war by US forces -- who launched their fourth strike in 24 hours on Thursday, killing six militants, according to officials.

Taliban militants have vowed to attack Pakistan security forces in retaliation for the drone attacks, which they say are carried out with the government's consent.

There have been several deadly attacks over the past week throughout the country -- with the Taliban claiming responsibility for Monday's suicide attack on a police station in the northwest that killed 19, and a triple suicide attack in the eastern city of Lahore last week that left 31 dead.

The last known journalist to be killed in the tribal northwest was in 2007, when the body of Pakistani reporter Hayatullah Khan was discovered near Mir Ali after he reported the death of alleged al-Qaeda commander Abu Hamza Rabia.

The mystery over the discovery of his bullet-riddled body came after Khan contradicted an official account of Rabia's death, saying he had been killed by a US missile -- not in a bomb-making accident as claimed by Pakistan.