Cheng Leung-chung, 19, and Lam Tai-kau, 18, pleaded guilty in the District Court to robbery and obtaining property by deception.

On December 1, Cheng accosted Cheung Pak-hing, 30, outside a Shun Tin 7-Eleven and told him to follow him into a nearby building, where he stripped him of $1,700.

On December 4, Pak-hing was on his way home after work when he was approached by Cheng and Lam.

The two men produced something resembling warrants and claimed to be police officers. They then asked Pak-hing to take out his money for 'registration'. He gave them $270 and they told him to leave.

Three days later, Pak-hing was ambushed by Lam and an accomplice outside the door to the flat he shared with his brother, Pak-sheung. The robbers forced the frightened man to let them inside and then instructed him to stand by the door while they ransacked his home. They made off with two watches, three cassette recorders and $3,500.

Eleven days later, on December 18, the twins were approached by Cheng and Lam, who again claimed to be police officers.

The robbers told the twins they had arrested a man suspected of being one of the bogus policemen who duped Pak-hing out of his money, and instructed the twins to accompany them into a nearby building.

The thieves then searched the twins, took their ID cards and the $3,400 they were carrying and left.

On January 3, the two thieves returned to the twins' home while Pak-hing was alone in the flat.

He answered a knock at the door and found himself face to face with the robbers. The pair barged in and told him to turn over all his money immediately. The victim handed them $280.

But his brother returned unexpectedly, startling the thieves into flight.

Following the robberies, Pak-sheung tried to commit suicide by throwing himself from a window.

Deputy Judge Line delayed sentencing until February 22 pending background reports.