The Foreign Office was investigating reports last night that two white British al-Qaida members had been killed in a drone attack in Pakistan. The Britons are said to have died in a Hellfire missile strike by a remote-controlled US Predator drone near the town of Datta Khel five days ago.

The militants, aged 48 and 25, using the pseudonyms Abu Bakr and Mansoor Ahmed, were apparently in a vehicle in the mountainous region with two other fighters at the time.

The Foreign Office said: "We are aware of media reports of the death of two British nationals in Pakistan. Our high commission in Pakistan is seeking further information on these reports."

If confirmed, the men, one of whom apparently originally had the name Steve, would be the first white British converts to have been killed in the area.

The pair came to Pakistan last year and travelled to a town in North Waziristan in the tribal belt bordering Afghanistan to join al-Qaida, Channel Four news reported.

Another British militant, Abdul Jabber, who was of Asian descent, died in September in a drone attack. Along with his brother, he was allegedly suspected of planning attacks on European cities.

There have been at least 25 US drone attacks in Pakistan since then, killing around 50 people. The tactic has been stepped up as the US attempts to tackle groups of fighters in Pakistani villages and compounds.

The strikes are not officially acknowledged by the CIA and are a subject of lively debate inside the US system, the WikiLeaks diplomatic cables have shown. Last year ambassador Anne Patterson argued that increased "unilateral operations" risked "destabilising the Pakistani state" and ultimately hindering the US goal of expelling al-Qaida from the region.

North Waziristan is home to hundreds of Pakistani and foreign Islamist militants, many belonging to or allied with al-Qaida and the Taliban. The region also hosts the Haqqani network, a powerful insurgent group that US officials say is behind many of the attacks on US and Nato forces across the border in Afghanistan.