SINGAPORE - At least 100 Chinese bus drivers in Singapore refused to go to work on Monday to protest against changes to their employment terms, media said.

The drivers, employed by public transport operator SMRT Corp, were unhappy about having to switch to a six-day work-week with higher pay from a five-day week.

The change meant less opportunity to earn overtime pay, the Chinese-language Lianhe Zaobao newspaper reported on its website.

Pictures published by Shin Min Daily News, another Chinese-language paper, showed drivers gathered on the grounds of a dormitory where they live, with policemen and vehicles belonging to riot police around the premises.

Lianhe Wanbao quoted a driver saying he now got about S$1,400 a month, down from more than S$2,000 a month when he could earn more by working on days off.

The Chinese drivers were also unhappy about being paid less than drivers from Singapore and Malaysia, it said.

A spokesman for SMRT declined to comment, saying the company was drafting a statement.

State broadcaster Channel NewsAsia quoted the firm saying that talks were being held with the drivers.

Singapore bus and underground railway company SMRT has said that strike action taken by some of its bus drivers over wages has gone into a second day.

The company said that some 60 drivers, all of whom were recruited from China, failed to turn up for work on Tuesday.

This follows similar action on Monday, when the company said that more than 100 drivers failed to turn up for work.

Industrial action does not happen very often in Singapore, and the last major strike took place in 1986.

SMRT held talks with the workers on Monday in an effort to resolve the issue.

Media reports stated that the Chinese drivers were unhappy with the amount of money they were being paid in comparison to those from other countries.

SMRT has been hiring foreign drivers to fill a shortage of positions in Singapore.

In an emailed statement the company said that it was continuing to keep communications open.

Singapore's Ministry of Manpower said it was closely monitoring the situation.