Hong Kong  - X-ray machines and extra security checks were being put in place Thursday to screen the thousands of passengers travelling between Hong Kong and China by train as security is tightened ahead of the Olympics in August.

From Saturday, passengers would have to arrive 15 minutes earlier - a full hour before departure - to clear security checks on the hourly trains travelling from Kowloon in Hong Kong to Guangzhou in southern China as well as to Beijing and Shanghai.

The X-ray machines are to screen all luggage before passengers get on cross-border trains, and extra security staff is to man checkpoints, Hong Kong's Mass Transit Railway Corp announced.

A company spokeswoman declined to say if the new security measures were linked to the Olympics, saying only that they were being upgraded to match heightened security on the Chinese side of the border.

The heightened security comes two months after tough new visa restrictions were placed upon foreigners entering China from Hong Kong, where many expatriates doing business in industrial southern China live.

Foreigners can no longer get multiple entry visas, meaning business people travelling regularly to China from Hong Kong have to queue up and apply repeatedly for single- and double-entry visas.

Overseas business chambers and consulates have protested the measures, saying they are making it hard for Hong Kong-based business people to work in China, but Beijing has refused so far to ease the restrictions. (dpa)