The US citizen said he was firing at the men in self-defence [AFP]

A US consular worker has been charged with the murder of two Pakistani men after they were shot dead in a busy street in Lahore.

The US citizen told police he shot the two motorcycle riders in self-defence after drew a gun on him in an attempted robbery, police officials told the AFP news agency.

"The American national told us he was driving his vehicle and stopped at a traffic signal. He saw motorcycle riders and one pulled out a pistol. The man told us he then pulled out his pistol and fired in self-defence," Aslam Tarin, the police chief, said.

Another Pakistani man was killed shortly after the shooting when a car from the US consulate in Lahore hit two pedestrians at the scene of the shooting, the police chief said.

Umar Saeed, a police officer at the scene, confirmed the details of the shooting and said the consular official had used a wireless radio device to call colleagues for help immediately after the shooting and a second consular car turned up to rescue him.

"Dozens of people gathered after the incident and tried to stop both the vehicles. Drivers of both the vehicles tried to flee the scene but police managed to stop them," Saeed said.

Murder charges

Atif Meraj, a police officer, said a murder case was officially registered against the consular worker as well as another case against two other Americans for killing the pedestrian.

The US state department confirmed that a US employee was involved in the incident in Lahore, but did not provide any details.

Local TV showed footage of what it said was the American's car, which had several bullet holes in the front windshield. It also showed one of the alleged attackers laying dead next to a motorbike with a pistol on the ground nearby.

The other man shot was shown being placed in the back of an ambulance and appeared to be wearing a holster.

More than 100 people blocked the road after the incident by setting tyres on fire to protest against the killing, an AFP reporter at the scene said.

The protest later moved to picket the police station where the car involved in the incident was impounded.

PJ Crowley, the US state department spokesman, said the US would try hard to ensure there is no anti-US backlash from what he deemed a "tragedy".

"We want to make sure that a tragedy like this does not affect the strategic partnership that we're building with Pakistan," he said.

"And we'll work as hard as we can to explain that to the Pakistani people."