The strike has highlighted affluent but tightly-controlled Singapore's heavy dependency on migrant labour to drive its economic growth amid falling birth rates.

The Ministry of Manpower said 29 drivers' work permits had been revoked and immigration officials "will be repatriating them" for involvement in a two-day stoppage to demand better pay and working conditions.

"The strike was planned and premeditated. It disrupted our public transport which is an essential service, and posed a threat to public order," its statement said.

A fifth driver has been arrested and will be charged in addition to four others who have been brought to court for allegedly instigating the November 26-27 work stoppage at state-linked transport firm SMRT.

If found guilty of involvement in an illegal strike, they could be jailed for up to a year or fined a maximum of Sg$2,000 ($1,640) -- the equivalent of two months' wages for a driver.

Strikes are illegal in Singapore for workers in "essential services" such as transport unless they give 14 days' prior notice and comply with other requirements.

"Barring any new developments, we do not expect further arrests or repatriations related to this illegal strike," the manpower ministry said.

"The police will be issuing warnings to the others who were involved, but no further action will be taken against them and they will be allowed to remain and work in Singapore, so long as they continue to abide by our laws."

The Chinese government has urged Singapore to respect the workers' legal rights while also cautioning its citizens to obey local laws.

A total of 171 drivers launched the strike by refusing to leave their dormitories to report for work, with the number falling to 88 on the second day. They issued no strike declaration or public statements.

The strikers were contract workers who did not belong to any union and were questioning why they were being paid less than their Malaysian counterparts for the same work.

SMRT has had to hire bus drivers from China and Malaysia due to a chronic labour shortage.

Singapore's last strike took place at a shipyard in 1986.

Unions have since cooperated with the government and private employers in a tripartite system to protect industrial harmony, attract foreign investment and negotiate wage increases and other benefits.

An SMRT spokesman told AFP that 22 percent of its 2,030 bus drivers were from China, another 22 percent from Malaysia and the rest Singaporean citizens and permanent residents.

The strikers drew scorn from Singaporeans complaining about their rebellious behaviour but also generated sympathy from others after their wages and living conditions were exposed by the walkout.

Sinapan Samydorai, director for Southeast Asian affairs at civil rights group Think Centre, criticised the government action as "a bit too harsh" and told AFP the drivers should have been let off with a stern warning as their grievances were real.

SMRT has promised to look into the strikers' demands, fumigate their bedbug-infested dormitory rooms, find alternative housing in 2013 and open permanent communication lines with its Chinese workers.

Singapore's opposition Workers' Party has issued a statement calling for fair treatment of foreign labourers.

"It is in Singapore's interests, and in line with our nation's values, that all workers are treated fairly, so that they are motivated to perform their jobs with excellence," it said.

"This is especially so for workers providing essential public services as it affects not just the local public but also Singapore's international reputation."