WASHINGTON: al Qaeda's second-in-command Abu Yahya al-Libi was the target of a US drone strike that killed 15 people in Pakistan's lawless tribal belt on Monday, US media reported.

US officials confirmed to The New York Times that Libi had been the target of the missile attack in North Waziristan, a Taliban and al Qaeda stronghold along the Afghan border, but could not say whether he had survived.

“People are looking very closely to see whether he's still alive,” a US official told the Times.

“It'll take some time for people to gain a high level of confidence that he's dead. But he's number two in al Qaeda, and this would be a major blow.” A senior US official also told ABC News that Libi had been the target of the attack, the third drone strike in as many days and the deadliest this year.

A senior Pakistani security source in Peshawar, meanwhile, told the Times that it “looks like he has been killed.” This would be a major blow to core al Qaeda - removing the number two leader twice in less than a year,” a senior US official told AFP, declining to confirm whether Libi was dead or alive.

“The degradation to core al Qaeda during the past several years has depleted the ranks to such an extent that there is now no clear successor to take on the breadth of his responsibilities, putting additional pressure on (Ayman al-) Zawahiri to try to manage the group in an effective way.”

The official, who spoke on condition of anonymity, noted that Libi had served as “general manager” for al Qaeda's main branch, overseeing its daily operations in Pakistani's lawless tribal regions and managing links to affiliates around the world.

Libi, a Libyan citizen believed to be in his late 40s, has been an influential al Qaeda commander. He became the international terror network's deputy leader after the August death of Atiyah abd al-Rahman, another Libyan national who was killed in a US missile strike in North Waziristan.

The militant leader, who has a $1 million US bounty on his head, was falsely reported dead previously, after a December 2009 drone strike in South Waziristan.

Pakistani officials said two missiles slammed into a compound in the village of Hesokhel, east of Miramshah, the capital of North Waziristan, before dawn.

A security official in Miramshah told AFP that the bodies of those killed could not be identified and that there were unconfirmed reports that foreigners were among the dead, a possible reference to al Qaeda fighters.

Should his death be confirmed, Libi would be among the highest profile al Qaeda militants killed by US forces since a Navy SEAL raid killed former leader Osama bin Laden in May 2011.

Libi was captured in 2002, after Nato forces toppled Afghanistan's Taliban rulers, and was held at the US high-security prison at Bagram Air Base. But he escaped three years later, giving him notoriety and credibility among militants.