The hour-long fracas on Sunday night, triggered when an Indian construction worker was struck and killed by a private bus in the Little India district, compelled Prime Minister Lee Hsien Loong to order the creation of a special committee to investigate the incident.

Police said about 400 people were involved in the riot, and that 27 South Asian workers had been arrested on charges punishable by up to seven years in prison as well as caning.

Lee said there could be "no excuse" for the rampage that left 39 police and civil defence staff injured, and 25 vehicles -- including 16 police cars -- damaged or torched.

"The riot was an isolated incident arising from the unlawful actions of an unruly mob reacting to a fatal traffic accident," Lee said in a statement.

"We must not allow this bad incident to tarnish our views of the foreign worker community here."

Lee added that the committee of inquiry to be convened by the interior ministry will review the factors that led to the riot, as well as existing measures to manage areas where foreign workers congregate.

Singapore is one of the wealthiest places in the world, but the island republic of 5.4 million people depends heavily on guest workers, with labourers from South Asia dominating sectors like construction.

Widely regarded as one of the world's safest societies, the city-state prides itself on social order and racial harmony, and many citizens expressed dismay over the mayhem.

"My God," a reader named Hayeden wrote on the Yahoo! Singapore website. "How can such a thing happen to my Singapore."

Prominent blogger Andrew Loh said Singaporeans were astonished as "we have not seen something of this scale before".

Police said the 27 men arrested were aged between 23 and 45, and included 24 Indian nationals, two Bangladeshis and one Singapore permanent resident.

Analysts played down suggestions that the riot, which was brought under control by elite police commandoes, could be an indication of wider discontent among poorly paid migrant workers.

Devadas Krishnadas, the founder and managing director of Future-Moves, a Singapore-based risk consultancy, said it was "an isolated incident where a variety of factors combined to blow matters out of hand".

"The fact that it involved foreign workers is incidental, not central, to the events," he wrote in a commentary for Singapore's Today newspaper.

"There is no justification to generalise the blame across any group, any race or any gender," he added.

The incident triggered online attacks on foreign workers, whose large presence has been a hot political topic in recent years. Others called for calm and warned against stoking racial hatred.

Jolovan Wham, an activist on migrant workers' welfare, said that "in the absence of sufficient information about the 'riot', it is difficult to determine if it is a symptom of pent-up rage".

The civil defence force said emergency workers who tried to extricate the man from under the private bus had been attacked by a crowd before a full-blown riot erupted.

The victim was identified as Sakthivel Kumaravelu, a 33-year-old who worked for a scaffolding company and was among the many migrant workers who congregate in Little India on Sundays.

Transport Minister Lui Tuck Yew, an MP for the affected district, said the cause of the riot was still unclear, but that "alcohol could have been a contributory factor".

There have already been calls to curb alcohol consumption in public places in the congested Little India precinct.

Resident Basher Marican, 69, who was returning home when the riot escalated, told AFP: "It was very unruly, I walked past a crowd along the restaurants. There were some who were cheering others as they attacked the bus."

He said the crowd was "clearly drunk" and that some were throwing bottles during the melee.

Sunday's violence was the first riot in Singapore since racial disturbances in 1969. Since then, the government has imposed strict controls on protests.

Ethnic Chinese make up 74 per cent of Singapore's resident population of 3.8 million, with Malay Muslims accounting for 13.3 per cent, followed by ethnic Indians, Eurasians and other racial groups.