Drugs worth more than $288,000 were seized in an operation by the Central Narcotics Bureau (CNB) on Monday.
The seized drugs include 1.93kg of heroin, 1.04kg of cannabis and 870g of "Ice" or methamphetamine.
Four suspected drug offenders - three Singaporeans and one Malaysian - were arrested, CNB said in a statement yesterday.
CNB officers were observing a 23-year-old Singaporean man, a suspected trafficker, in Eunos Crescent on Monday afternoon. He was with a Singaporean woman, also 23, who was a suspected drug abuser. He was spotted meeting another suspect, a 23-year-old Malaysian man.
The Singaporean man and woman were later arrested at a carpark in Ubi Avenue 2. The man "put up a violent struggle to resist arrest", CNB said. A jackknife, a large knife with a folding blade, was recovered from him during the arrest.
A search of his car uncovered 985g of heroin, 1,038g of cannabis and 192g of "Ice".
Meanwhile, another group of CNB officers tracked the Malaysian and arrested him at the junction of Jalan Eunos and Changi Road. A total of 466g of heroin, 678g of "Ice" and cash amounting to $25,400 were recovered from the Malaysian and his motorcycle.
Another party of officers apprehended a 58-year-old Singaporean man, a suspected trafficker believed to be associated with the Malaysian, near Block 10 North Bridge Road. About 468g of heroin was recovered from his bag, while 12g of heroin was recovered from his pocket.
Investigations are ongoing.
The 1.93kg of heroin seized in this operation is enough to feed the addiction of about 919 abusers for a week, CNB said.