Speaking at a press conference in Lahore, Aslam Tareen said eyewitness accounts and forensic reports have shown that Davis did not shoot the two young men in self-defense.

He said according to an eyewitness one of the young men on the motorbike started running when Davis opened fire but that he was also shot.

“Davis’ plea has been rejected by police investigators,” Tareen said. “We have proof Davis did not act in self-defense. He committed cold-blooded murder.”

The police chief said investigators have recovered a GPS tracker, mobile phones, wireless sets, a survival kit and photographs from Davis’ car.

The police chief said Davis told interrogators that one of the Pakistani men had pointed his pistol at him.

However, Tareen said the slain man's pistol had been examined and officers found that all the bullets were in the magazine and no bullet was found in the chamber.

The police chief said the issue of diplomatic immunity was a government matter but that the police have sent a preliminary charge sheet recommending Davis face a murder trial.

In another development, a judge ordered the man's detention extended for 14 days in a local jail and told the Pakistani government to clarify if he has diplomatic immunity. The next hearing will be on Feb. 25.

The US says Davis shot two Pakistanis because they were trying to rob him in the eastern city of Lahore. Washington insists his detention is illegal under international agreements covering diplomats because he was a US Embassy staffer, and American officials have begun curbing diplomatic contacts and threatening to cut off billions in aid to Pakistan if he is not freed.

Pakistani leaders — loathe to incur a backlash in a public already rife with anti-US sentiment — have for days avoided making definitive statements on Davis' legal status, instead saying the issue is up to the courts.

According to The Associated Press, Courtney Beale, a US Embassy spokeswoman said, “We regret that this incident resulted in loss of life, however eyewitness reports on the day of the incident showed the American diplomat acted in self-defense. There is no doubt he has diplomatic immunity, and we are working with the government of Pakistan to resolve the issue.”

Davis will be held in a well-protected cell kept for special detainees, said two officials at the jail who requested anonymity because of the sensitivity of the subject, The Associated Press said.

Exactly what sort of work Davis does for the US is a major issue because it could affect Pakistani determination about his diplomatic immunity. US officials in Islamabad will say only that he was an American Embassy employee who was considered part of the “administrative and technical staff.” That designation gives him blanket immunity, the US says.

There has also been controversy in Pakistan over the fact that Davis was armed. A senior US official has told The Associated Press that Davis was authorized by the United States to carry a weapon, but that it was a “gray area” whether Pakistani law permitted him to do so.