Malaysia is willing to use strict security laws to curb street protests, Prime Minister Abdullah Badawi says.
Police dowsed protesters with water at the weekend
He suggested the Internal Security Act (ISA), which allows indefinite detention without trial, could be used.
His comments follow one of the largest demonstrations against the authorities in a decade, which took place this weekend in defiance of government bans.
Thousands of ethnic Indians took the streets, aggrieved at alleged discrimination by the majority Malays.
The ISA was originally put in place at the end of the British colonial era, to fight the perceived communist threat.
It has been controversial ever since, with rights groups claiming that more than 70 people are currently detained without trial under its powers - some for more than six years.
Malaysia's state-run Bernama news agency quoted Mr Abdullah as saying: "The ISA is a preventive measure to spare the nation from untoward incidents that can harm the prevailing peace and harmony and create all sorts of adverse things.
"When it is appropriate to use it, it will be used."
Bernama said the prime minister had made his comments in response to reports that several more demonstrations were to be held soon.
The agency did not give further details of the planned protests.