United States spy agency Central Investigation Agency has been operating a secret drone-base from Saudi Arabia for the last two years to conduct lethal strikes against the Yemen-based terror outfit -- Al Qaeda in the Arabian Peninsula.
A drone flown from there was used in September 2011 to kill Anwar al-Awlaki, a US-born cleric who was alleged to be the AQAP's external operations chief, according to a report.
US media have known of its existence since then, but have not reported it.
Explaining their position, top Obama administration officials had said they were concerned that disclosure would undermine operations against the AQAP. They said the move also may damage counter-terrorism collaboration with Saudi Arabia, a close US ally.
The US military pulled out virtually all of its soldiers from Saudi Arabia in 2003, having stationed between 5,000 and 10,000 troops in the Gulf nation after the 1991 Gulf war. However, the location of the secret drone base was not revealed.
Construction was ordered after a December 2009 cruise missile strike in Yemen, the New York Times reported. It was the first strike ordered by the Obama administration, and ended in disaster, with dozens of civilians, including women and children, killed.
US officials told the Times that the first time the CIA used the secret facility was to kill Awlaki.
Since then, the CIA has been "given the mission of hunting and killing 'high-value targets' in Yemen" -- the leaders of AQAP who government lawyers had determined posed a direct threat to the US -- the officials added.
Three other Americans, including Awlaki's 16-year-old son, have also been killed in US strikes in Yemen, which can reportedly be carried out without the permission of the country's government.
Kristian Coates-Ulrichsen, an expert on Gulf politics at the London School of Economics, said Saudi anxieties about the growing threat of the AQAP would have been behind the government's decision to allow the US to fly drones from inside the kingdom.
"The Saudis see the AQAP as a very real threat to their domestic security," Kristian told the BBC.