LAHORE: A court on Thursday extended the detention of a US government employee for eight more days pending investigation of a double murder in Lahore.

The US consular employee, whom Pakistani police have identified as Raymond Davis, was arrested a week ago for shooting dead two motorcyclists in self-defence, fearing that they were about to rob him.

A third Pakistani was run over and killed by a vehicle from the local US consulate that tried to come to Davis' assistance.

Washington is demanding the man's release, saying he has diplomatic immunity, as tempers run high in Pakistan over the incident.

“We produced the American in the court of magistrate Zafar Iqbal, who extended his remand in police custody to another eight days,” public prosecutor Abdul Samad told AFP.

Police have registered a case of double murder against the American and Samad said he would be produced next in court on February 11.

The deaths sparked huge controversy in Pakistan, where anti-Americanism runs high, fuelled by the government's unpopular alliance with Washington, the war in Afghanistan and US missile attacks in the northwest.

Washington insists the American is entitled to diplomatic immunity and is therefore being held unlawfully by the Pakistani authorities.

It also supports his version of events that he was confronted by two armed men on motorcycles whom he had reason to believe meant him bodily harm, meaning that he acted in legitimate self-defence.

Another court blocked any move to extradite him. Relatives of the three Pakistanis who died in the incident on January 27 are to demonstrate outside the US consulate in Lahore later Thursday.

But Interior Minister Rehman Malik has now confirmed the American has a diplomatic passport and cautioned the media against “hyped” coverage that does not represent the facts, opening the doors to his possible release.

“The file is with me and whenever the high court needs this file, the file will be presented to the court.

“Don't do misreporting based on presumptions; let's not hype (the issue). We will provide whatever information the court requires,” he told reporters.

Davis was brought to court 30 minutes ahead of the scheduled hearing under tight security with the media kept at a distance.

Armed police cordoned off the court and the American arrived in an armoured personnel carrier, an AFP reporter said.

Relatives of the victims have demanded that the government try Davis under terror charges. Activists and family members on Wednesday shouted “hang Davis” at the scene of the shooting.

Questions remain unanswered about why the American was driving around Lahore with a gun and US officials have refused to confirm his name.

Police told AFP they recovered a Glock pistol, four loaded magazines, a GPS navigation system and small telescope from his car.

On the two Pakistanis, police found two pistols, magazine belts and four mobile phones, at least two of which they believe could have been stolen, an officer said on condition of anonymity.

The officer described one of them as a street robber “wanted” in connection with three or four incidents and the other as his accomplice.