Lee Hsien Loong calls for citizens not to show animosity towards migrant workers as police arrest 24 Indian citizens over riots

Singapore's prime minister has urged citizens not to show animosity towards migrant workers following the first rioting in 40 years in the wealthy state, which prides itself on being an island of calm in an often chaotic region.

The disorder involved mostly Indian guest workers and broke out in the Little India district on Sunday night after an Indian worker was hit and killed by a bus driven by a Singaporean. Cars were set alight and 18 people injured as crowds hurled stones at authorities.

It followed recent signs of tensions between citizens and the growing numbers of migrant workers, who have provided the bulk of the workforce constructing the country's impressive skyline, transport and other infrastructure. About a quarter of Singapore's 5.4 million residents are transient workers, compared with a tenth in 1990, according to government statistics.

In a posting on his Facebook page on Monday, the prime minister, Lee Hsien Loong, said: "The vast majority of foreign workers here obey our laws. We must not let this bad incident tarnish our views of workers here. Nor should we condone hateful or xenophobic comments, especially online."

Liberal commentators said the riot strengthened their calls for better treatment of the workers. Roy Ngerng, a blogger on social issues, said: "The inequality that has taken root in Singapore has dire consequences and they are beginning to show.

"Perhaps it is to be expected that when we pay such [a] pittance ... to people who have helped build our country – our buildings and roads – and yet expect them to toil in the most tiresome conditions."

Police said Indian citizens comprised 24 of the 27 people arrested so far, while two others were Bangladeshis and another was a person of undisclosed origin with Singaporean permanent residency status. Rioting in Singapore can be punished by seven years in prison and whipping with a cane.

One cabinet minister suggested that alcohol licences should be more tightly restricted in Little India. The transport minister Lui Tuck Yew, whose constituency includes Little India, said it was "quite evident ... alcohol could have been a contributory factor" based on his observation of some of those arrested, the Straits Times newspaper reported.

Sunday night's incident is regarded as Singapore's worst outbreak of public violence since race riots in 1964 involving the ethnic Chinese majority and Malay minority left 36 people dead that year.