WASHINGTON: The United States called Monday for Pakistan to free an American arrested for killing two men and to ensure his safety in custody after revelations he worked for the CIA.

US officials declined public comment on accounts that Raymond Davis worked for the Central Intelligence agency and insisted he enjoyed diplomatic immunity because Pakistan had accepted his status when he entered.

“We remain concerned about him and our message to Pakistan remains he should be released as soon as possible,” State Department spokesman Philip Crowley told reporters on a conference call.

Crowley said Pakistan has told the United States that Davis is staying “in the safest possible location in Lahore,” the eastern city where he shot dead two Pakistani men on January 27.

“Clearly, we hold the government of Pakistan fully responsible for his safety,” Crowley said.

The New York Times on Monday reported that Davis was part of a CIA operation tracking Islamic extremists in eastern Pakistan such as Lashkar-e-Taiba, the virulently anti-Indian group involved in the bloody 2008 siege of Mumbai.

The New York Times said it withheld the information after President Barack Obama's administration said it would endanger Davis' safety, but decided to release the details after other media reported the CIA link.