The leader of al Qaeda's branch in Yemen was targeted in a CIA drone strike last week, though US officials would not immediately confirm he had been killed, The Washington Post reported.
Nasir al-Wuhayshi's group, al Qaeda in the Arabian Peninsula, is behind several plots against the US, including an attempt to blow up a commercial airliner on Christmas Day 2009.
US officials told the Post they were reviewing intelligence linked to a June 9 drone strike that targeted Wuhayshi, who was also named al Qaeda's number two, and other AQAP operatives.
"We are looking to confirm his death," a US intelligence official told the newspaper on Monday.
CNN, meanwhile, cited two Yemeni national security officials as saying Wuhayshi had been killed on Friday.
A Yemeni official last week told AFP that a drone had fired four missiles on June 9 at three al Qaeda militants, including an unnamed "leading figure," near Mukalla port, killing them on the spot.
The US government had a $10 million reward for any information leading to his capture or killing.
A former aide to al Qaeda's late founder Osama bin Laden, Wuhayshi attended the group's Al-Farouk training camp in Afghanistan in the late 1990s. He is said to have fled Afghanistan in 2002 to Iran, where he was arrested and handed over to Yemen. There he was held without charge until he escaped by tunneling his way out with 22 other prisoners in February 2006.
In 2007, Wuhayshi was named head of al Qaeda in Yemen.
When Bin Laden was killed by US commandos in May 2010 in Pakistan, Wuhayshi warned the Americans not to fool themselves that the fight would end with the al Qaeda chief's demise.
"What is coming is greater and worse, and what is awaiting you is more intense and harmful," he said.
AQAP has exploited months of fighting in Yemen between Iran-backed rebels and their Saudi-backed rivals to consolidate its grip on Hadramawt's provincial capital Mukalla - a city of more than 200,000.
The United States considers AQAP the extremist group's deadliest global franchise and regularly targets its militants with armed drone strikes on Yemeni territory.
It is the only government that operates the unmanned aircraft over the impoverished country.