The riot broke out in Little India after a pedestrian was knocked down by a private bus and killed Sunday night.
Police said in a statement that the accident occurred at the junction of Race Course Road and Hampshire Road at about 9.25pm.
The statement said that a riot then broke out, involving about 400 people.
They damaged five police vehicles and several private vehicles.
Police later said in a press conference that 27 people, all of South Asian descent, had been arrested. Eighteen people, including 10 police officers and four Singapore Civil Defence Force (SCDF) officers, were taken to hospital with injuries.
The New Paper learnt that the driver of the private bus was dragged out and assaulted by a group of people.
His colleague, Madam Wong Gek Woon, 38, was cowering at the back of the bus as the angry mob smashed the windows and tried to hoist themselves into the vehicle to get to its occupants.
Her husband, Mr Alan Wee, 50, told TNP at Tan Tock Seng Hospital (TTSH) early this morning that she coordinates the buses for the company and was in Little India when someone told her one of its buses had been involved in an accident.
The bus was filled with workers being taken back to their dormitory.
Mr Wee said she went to check and someone told her to get into the bus as it was getting dangerous.
He said she called him as the bus came under attack. She told him the driver had a serious neck injury and his clothes were stained with blood.
Mr Wee said he rushed to the scene and his wife was escorted out of the bus by six police officers.
She is in stable condition and was kept under observation at TTSH, he said. Police said that men from the Special Operations Command and Gurkha Contingent were deployed to Little India to tackle the riot and the situation was under control.
Police advised members of the public in the area to remain indoors while police operations were ongoing. Others should stay away from the area.
They also advised the public to stay calm and not to speculate on the incident.
Those with any information about the riot should call the police at 1800-255- 0000.
Deputy Prime Minister and Home Affairs Minister Teo Chee Hean said: "This is a serious incident which has resulted in injuries and damage to public property.
"The situation is now under control. Police will spare no efforts to apprehend the subjects involved in the riot."
The SCDF said in a statement at 1.40am today that when its officers arrived at the scene, they found a man trapped under a bus.
A paramedic pronounced him dead and SCDF rescuers extricated the body using hydraulic rescue equipment.
Projectiles were thrown at them while they were extricating the body.
The statement said nine SCDF vehicles were damaged in the incident.
At press time, the SCDF had taken 18 casualties to TTSH.
When TNP arrived at the hospital just after midnight, several people had gathered at the accident and emergency (A&E) department.
Dozens of uniformed and plain clothes police officers were nearby.
Witnesses told TNP there was a surge of casualties between 10.30pm and 11.30pm.
A man who declined to be named said he saw several police cars bringing injured police officers with their heads and faces bandaged to the A&E department.
"It was very bad. I have never seen anything like that before," he said.
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