The other police officer, aged 28, had received injuries to his face and legs. On Friday afternoon, he remained in critical condition at the intensive care unit of the hospital.

Police Commissioner Dick Lee Ming-kwai told reporters that at least 10 bullets had been fired.

He revealed that police identity documents were found on the gunman.

?At this stage, we suspect the man could also be a police officer,? Mr Lee said.

Three pistols, two belonging to the patrolling officers and one similar to a police revolver, were found at scene, police said.

It is not clear exactly how the shootout unfolded ? police officers on Friday afternoon were still investigating.

It is believed to have started after the two patrolling officers intercepted the gunman, who had been seen acting suspiciously.

After the shootout, dozens of police officers cordoned off the scene for forensic experts to collect evidence. Local TV showed detectives extracting fingerprints on the handrails of the subway.

Mr Lee said the subway?s location was secluded and few people were using it.

Local radio quoted police sources as saying the gunman was a constable who was stationed in Tung Chung on Lantau Island. The sources said one of the handguns might have links to the death of police constable Leung Shing-yan, five years ago.

Leung was shot dead, with his service revolver and six rounds of ammunition stolen, in March 2001 while on duty.

A police spokesman appealed to the public who had witnessed the case and who might have information to contact officers on: tel: 2860-8366.