PM warns protesters he is ready to sacrifice freedoms for national stability.
The ISA provides for an initial detention of 60 days without trial followed by a maximum of two years at a detention centre in Taiping in the northern state of Perak, about 300 kilometres from Kuala Lumpur.
The two-year detention can be extended indefinitely by a ministerial order.
On November 25, Hindraf led a rally of several thousand ethnic Indians in Kuala Lumpur to protest against what they say are discriminatory government policies.
The protest was broken up by police using tear gas and water cannon.
The government has rejected the claims of discrimination and warned such protests risk inflaming Malaysia‘s fragile racial relations.
The rally followed another protest two weeks earlier to demand electoral reforms ahead of a national election widely expected to be called in 2008.
That protest was also broken up by police.
The government bans public assemblies on grounds that gatherings that are held without a police permit could disrupt Malaysia‘s fragile racial balance.