The US embassy in Pakistan has called for "the immediate release" of an American charged with murdering two Pakistanis in the city of Lahore.
The embassy said the man had US diplomatic status and therefore was immune from prosecution.
"The diplomat acted in self-defence when confronted by two armed men on motorcycles" on 27 January, it added.
The man - identified in Pakistan as Raymond Davis - was charged with the murder of the two men on Friday.
He told the court in Lahore that he had fired his gun in self-defence.
Another person was run over and killed by a vehicle carrying Mr Davis' colleagues as they came to his aid, police and witnesses have said.
Magistrates have remanded Mr Davis in custody until next week, while police investigate the shooting."The United States Embassy in Pakistan calls for the immediate release of a US diplomat unlawfully detained by authorities in Lahore," the embassy said in a statement on Saturday.
"The diplomat, assigned to the US Embassy in Islamabad, has a US diplomatic passport and Pakistani visa valid until June 2012.
"When detained, the US diplomat identified himself to police as a diplomat and repeatedly requested immunity under the Vienna Convention on Diplomatic Relations. Local police and senior authorities failed to observe their legal obligation to verify his status.