The Central Intelligence Agency (CIA) has secretly been using an airbase in southwestern Pakistan to launch the predator drones to attack the militants within the country, a report said.
Both Pakistan and US governments have repeatedly denied that Washington is conducting military operations, covert or otherwise, on Pakistani territory.
But The Times on Wednesday report says that it has discovered that the CIA has been using the Shamsi airfield, 30 miles from the Afghan border, in the southwestern province of Baluchistan for at least a year.
The strip allows US forces to launch a drone within minutes of receiving actionable intelligence as well as allowing them to attack targets further afield, the report said.
The report quoted Major General Athar Abbas, chief military spokesman, confirming that US forces were using Shamsi adding that "The airfield is being used only for logistics."
"The Americans were also using another airbase near Jacobabad, 300 miles northeast of Karachi, for logistics and military operations", the report quoted Abbas as saying.
"We can see the planes flying from the base. The area around the base is a high-security zone and no one is allowed there." Safar Khan, a local journalist in Shamsi said.
The key to The Times investigation was an unexplained delivery of 730,000 gallons of F34 aviation fuel to Shamsi airfield, details of which were found on the Pentagon's fuel procurement agency website.
The Defence Energy Support Centre site shows that a civilian company, Nordic Camp Supply (NCS), was contracted to deliver the fuel worth $3.2 million from Pakistan Refineries near Karachi.
However, the newspaper also quoted a spokesman for the US embassy in Pakistan denying that US forces were based in Pakistan, but added that he could not comment on CIA operations.
Pakistan reportedly gave America permission to use Shamsi, Jacobabad and two other bases — Pasni and Dalbadin — for the invasion of Afghanistan in October 2001.
According to The Times investigation, Jacobabad became the main US airbase until Bagram, near Kabul, was repaired, while Pasni was used for helicopters and Dalbadin as a refuelling post for special force's helicopters.
However, it added that in December 2001, Pakistan began sharing Jacobabad and Pasni airfield with US forces.
And in July 2006 the Pakistani government reportedly declared that America was no longer using Shamsi, Pasni and Jacobabad, although they were at its disposal in an emergency.
Meanwhile Pakistani government has repeatedly demanded that the US should halt drone attacks on northern tribal areas that it says have caused hundreds of civilian casualties and fuelled anti-American sentiment.
The latest drone strike on Monday — the fourth since Barack Obama took assumed office —reportedly killed 31 people in the tribal agency of Kurram.