LAHORE, Pakistan >> An American CIA employee accused of murdering two Pakistanis appeared handcuffed in a Pakistani court today, where he refused to sign a charge sheet after claiming diplomatic immunity, officials said.

The detention of Raymond Allen Davis has severely frayed ties between the U.S. and Pakistan, whose counterterrorism alliance is considered a crucial part of ending the war in Afghanistan.

Washington insists Davis is immune from prosecution because he is listed as a U.S. Embassy staff member. It says Davis shot two Pakistanis in self-defense when they tried to rob him in late January in the eastern city of Lahore.

Pakistani officials, wary of a backlash in a population rife with anti-American sentiment, have declined to confirm whether Davis has diplomatic immunity, saying the matter is up to the courts.

During today’s hearing, which was held in a Lahore jail and closed to the public, prosecutors tried to present the handcuffed Davis with a charge sheet.

The judge also asked whether Davis had engaged a defense attorney, according to Asad Manzoor Butt, a lawyer for a Pakistani bystander who was killed when struck by an American car rushing to assist Davis after the shootings.

But Davis refused to sign the charge sheet and said he did not want to participate in the case because he has immunity from prosecution under international agreements covering diplomats, said Butt, who attended the hearing.

The question of whether Davis has immunity is also being considered by the Lahore High Court.

Prosecutor Abdus Samad said Davis would be formally charged on March 3 at the next hearing.

The U.S. Embassy declined to immediately comment, though a spokeswoman confirmed that representatives of the U.S. consulate in Lahore were present at the hearing. Prosecutors could not immediately be reached after the hearing.

Davis is a 36-year-old Virginia native. U.S. officials speaking on condition of anonymity have acknowledged that he did security work as a contractor for the CIA, but was apparently in Pakistan under a diplomatic cover.

American officials, nonetheless, say his exact job has no bearing on whether he qualifies for diplomatic immunity based on their readings of international agreements. They say they notified the Pakistani government of his official position as an “administrative and technical staff” member of the embassy more than a year ago.

Meanwhile, police in northwest Pakistan said they had arrested an American staying in the area on an expired visa.

The man was detained today in the main northwestern city of Peshawar, said police officer Haroon Khan.

Khan identified the American as Aaron Mark DeHaven and said he was from West Virginia. It was not clear what he was doing in Pakistan.

The U.S. Embassy said it was looking into the case.