Pakistani security officials expressed doubt on Sunday over reports from the United States that it had killed the Al-Qaeda second-in-command near the Afghan border.

A senior US official said on Saturday that Atiyah abd al-Rahman had been killed in the northwest tribal area of Waziristan on August 22, without divulging the circumstances of his death.

However, local officials in the region told AFP last week that a US drone strike in North Waziristan on that date had killed at least four militants. It was not clear if the two incidents were connected.

A senior Pakistani security official in Peshawar told AFP: "We have checked this news report with informers and have worked on it. I doubt the authenticity of this news."

Another security official in Miranshah, the main town in North Waziristan, said he had received no information on the killing.

"For me it is just a rumour. Frankly speaking, we are even not aware that a man with this name is working as deputy chief of Al-Qaeda," he added.

The officials said the remote, mountainous area, just four kilometres (2.5 miles) from the Afghan border, is inaccessible.

"In such cases we rely on information sent from informers. We have not received any type of such a report," the security official in Mir Ali town, North Waziristan, told AFP.

An Afghan Taliban commander in Pakistan's northwestern tribal region who is in regular contact with Al-Qaeda described the news report as fake.

"It is a fake story. It's not true," he told AFP from an undisclosed location.

According to US authorities, Rahman, who was in his late 30s and Libyan, was appointed by Osama bin Laden and was Al-Qaeda's emissary in Iran, recruiting and facilitating talks with other Islamic groups.

He joined bin Laden in Afghanistan as a teenager in the 1980s to fight the Soviet Union.

Washington has called Pakistan's semi-autonomous northwest tribal region the global headquarters of Al-Qaeda, where Taliban and other Al-Qaeda-linked networks have rear bases from which they launch attacks on NATO forces in Afghanistan.

Although the United States does not publicly confirm drone attacks, its military and the CIA in Afghanistan are the only forces that deploy the unmanned Predator aircraft in the region.