The decapitated body of a woman was found floating in Whampoa River on Thursday morning.
Police said they received a call at 7.33am, after a jogger and a cleaner saw part of the body - wrapped in what appeared to be trash bags - in the waterway between McNair and St George's roads just after sunrise.
Singapore Civil Defence Force (SCDF) firefighters, who were called to the scene minutes later, then retrieved the body.
The Straits Times understands that the woman was wearing just a pair of black pants when her body was brought to land.
Details about the woman, whose arms were also thought to have been mutilated, are scant because no identification was found on her.
Police have classified the case as an unnatural death and are investigating.
When The Straits Times visited the scene later in the morning, SCDF divers were spotted searching the river at low tide. Police officers were also seen combing the area and searching rubbish bins in the neighbourhood for evidence.
The head of the woman, however, had not been found at press time.
Residents in the area were stunned to learn about Thursday's grisly find.