Local police arrested six men early on Tuesday morning in connection with Saturday evening's armed robbery of a bus on a major expressway.

Three men, all surnamed Chen, pleaded guilty to being involved in the robbery, while three others were held on suspicion of sheltering the men, a spokesman for Shenzhen Public Security Bureau told a press briefing yesterday.

However, two robbers remain at large, he warned.

The five-member gang raided an intercity bus at about 7 pm on Saturday and robbed 38 passengers, including 32 Hong Kong people.

They were carrying weapons during the attack.

The bus provides free transport mainly for Hong Kong people travelling from Shenzhen to their homes in a big residential community in Panyu District of Guangzhou, south China's Guangdong Province.

As the bus approached the Tiger Back (Hubei) tunnel on the Guangzhou-Shenzhen (Guangshen) expressway, near Shenzhen airport, a man signalled to the driver to pull over. When he stopped, four men boarded the bus.

They took away 18,500 yuan (US$2,312) and HK$59,000 (US$7,564) in cash, 34 mobile phones and some watches, rings and necklaces, the spokesman said. None of the passengers were hurt.

"Obviously, the suspects had prepared the raid for a long time and worked out the best time and place to do it, as well as a good escape route," Yu Xinguo, the spokesman, told reporters.

All five suspects, with the oldest aged 31, are believed to be from Taishan in the west of the province, Yu said.

The case has aroused the concern of central and local authorities, who have urged local police to solve it as soon as possible.

Yu said Shenzhen police would co-operate with police forces of neighbouring cities to crack down on expressway bus robbery.

The local police will also intensify patrols along the expressway and install electronic monitoring systems at bus terminals, inside buses and along the expressway, he noted.

(China Daily June 7, 2006)