Malaysian opposition and human rights activists said have gone on hunger strike in support of six detained opposition activists who are refusing food in jail.
The detainees, held since last April under the Internal Security Act (ISA) which allows detention without trial, have refused food since Wednesday in protest against their detention at the Kamunting Camp in northern Malaysia.
Opposition supporter Raja Petra Raja Kamaruddin said: "This is not a suicide mission. This is only a protest".
Surrounded by protest banners and sitting under makeshift tents, he and some 15 fellow hunger strikers are camping out outside the head office of the country's largest opposition party, Parti Islam se-Malaysia (PAS).
Mr Ezam Mohd Nor, one of the detainees, has said the anti-ISA campaign was aimed at embarrassing Prime Minister Mr Mahathir Mohamad ahead of his first visit to the White House since 1994.
President Bush has invited Mr Mahathir, who is widely seen as a strong, moderate Muslim leader, to visit him in May.
Malaysia's opposition leader and PAS chief Mr Fadzil Noor called on the government to free the six, whom he called political prisoners .
On Wednesday, non-governmental organisations and opposition groups marked the first anniversary of the detention of the six with a call for authorities to charge or free them, and to scrap the sweeping security law.