|A lawsuit aims to win $500 million in compensation for loss of life in drone strikes allegedly by the CIA [REUTERS]
The CIA has pulled its top spy out of Pakistan after "terrorists" threatened to kill him, US officials said.
The unusual move exposes growing complications on the front lines of the fight against al-Qaeda.
The CIA station chief was in transit on Thursday after a Pakistani lawsuit earlier this month accused him of killing civilians in missile strikes carried out by suspected US drones.
The lawsuit listed a name for the station chief, but the AP news agency has said that name is not authentic. AP did not publish the station chief's name because he remains undercover, and his name is classified.
CIA air strikes from unmanned aircraft have killed Taliban and al-Qaeda leaders and fighters, but have led to accusations in Pakistan that the strikes kill innocent people.
The US does not acknowledge the missile strikes, but there have been more than 100 such attacks this year - more than double the amount in 2009.
The lawsuit blew the American spy's cover, leading to threats against him and forcing the US to call him home, the officials said, speaking on condition of anonymity because of the sensitivity of the issue.
"Our station chiefs routinely encounter major risk as they work to keep America safe, and they've been targeted by terrorists in the past," George Little, CIA spokesman, said.
"They are courageous in the face of danger, and their security is obviously a top priority for the CIA, especially when there's an imminent threat."
Suing the CIA
The Pakistani lawsuit also named Leon Panetta, CIA director, and Robert Gates, US defence secretary.
Demonstrators in the heart of the capital, Islamabad, have carried placards bearing the officer's name as listed in the lawsuit and urging him to leave the country.
Shahzad Akbar, the lawyer bringing the case, said he got the name listed in the lawsuit from local journalists. He said he included the name because he wanted to sue a CIA operative living within the jurisdiction of the Islamabad court.
A Pakistani intelligence officer said the ISI, the country's intelligence service, knew the identity of the station chief, but had "no clue" how the name listed in the lawsuit was leaked.
The officer spoke on condition of anonymity because his agency, like many around the world, does not allow its operatives to be named in the media.
The CIA's work is unusually difficult in Pakistan, one of the United States' most important and at times frustrating counterterrorism allies.
The station chief in Islamabad operates as a secret general in the US war against terrorism. He runs the predator drone program targeting enemy fighters, handles some of the CIA's most urgent and sensitive tips and collaborates closely with Pakistan's ISI, one of the most important relationships in the spy world.
Al Jazeera's Kamal Hyder, reporting from Islamabad, said the ISI slammed rumours that it was involved in the leaking of the US spy's name.
"The intelligence agency [ISI] is also warning that such unfounded reports as they claim are likely to mar relations between the ISI and CIA," he said.
Almost a year ago, seven CIA officers and contractors were killed when a suicide bomber attacked a CIA base in Khost, Afghanistan. Six other agency officers were wounded in the attack, one of the deadliest in CIA history.
It is rare for a CIA station chief to see his cover blown.
In 1999, an Israeli newspaper revealed the identity of the station chief in Tel Aviv. In 2001, an Argentine newspaper printed a picture of the Buenos Aires station chief and details about him. In both instances, the station chiefs were recalled to the US.