KUALA LUMPUR, Jan 13 (AFP) - Human rights groups and media watchdogs Thursday condemned the arrest of four Malaysian opposition figures on sedition charges, saying they feared the start of a crackdown against political activists.

They pressed for the charges to be dropped, with one group accusing Malaysia of breaching international laws with the use of "strong-arm tactics to silence its critics."

National Justice Party (Keadilan) vice-president Marina Yusof and Democratic Action Party (DAP) deputy chairman Karpal Singh surrendered to police Wednesday after arrest warrants were issued under the Sedition Act.

Similar warrents were served on Zulkifli Sulong, editor of the Harakah newspaper owned by Parti Islam SeMalaysia (PAS), and the paper's publisher Chia Lim Thye. All four were released on bail.

The arrests took place just hours after Prime Minister Mahathir Mohamad left for a two-week vacation abroad and were the first after the November 29 general elections which saw the premier consolidating his position.

The official Bernama news agency said Zulkifli and Chia pleaded not guilty in separate courts Thursday to publishing a seditious article in August on an alleged conspiracy by Mahathir and his cronies against jailed ex-deputy premier Anwar Ibrahim.

They were granted bail, with Zulkifli's hearing fixed for May 22 and Chia's case to be mentioned on January 31. The two, along with Marina and Karpal who are to be charged Friday, face a fine of 5,000 ringit (1,316 dollars), a three-year jail term or both if convicted.

DAP chairman Lim Kit Siang said the police action was part of a crackdown against the opposition. Keadilan deputy president Chandra Muzaffar accused the government of using the Sedition Act to stiffle dissent, "intimidate the people and to browbeat them into servile submission to authority."

Charging Karpal, a lawyer for Anwar, for a statement he made in court last year during Anwar's sodomy trial was an "affront to the entire system of justice itself," he said.

But Deputy Premier and Home Minister Abdullah Ahmad Badawi, quoted by The Sun, said the arrests followed a thorough police investigation and were "not a crackdown."

He denied the action amounted to suppression of free speech, saying: "Anyone can say what they want about anything but there are also laws. It is necessary for us to respect the law."

The New York-based Lawyers Committee for Human Rights in a statement said Malaysia "has again resorted to strong-arm tactics to silence its critics, rather than playing by the rules of international law."

It said Karpal was the second Anwar lawyer to be punished for critical comments in a legal proceeding after Zainur Zakaria was charged with contempt for alleging prosecutors tried to fabricate evidence.

"This arrest is another in a series of attacks against lawyers willing to represent disfavoured clients like Anwar," said its director Robert Varenik.

"This type of action illustrates the government's unwillingness to play by the rules of free speech and access to lawyers enshrined in international law."

Malaysian rights group SUARAM feared the arrests signalled the "beginning of a bigger crackdown on opposition and political activitists" and showed the government's "utter intolerance for criticism."

Another local rights group ALIRAN said the fact no immediate charges were brought against the four suggested the move was "politically motivated."

Paris-based Reporters Sans Frontieries said the sedition charge against Zulkifli "constitutes a further step in the government's policy of gagging the opposition press."

The Bangkok-based Southeast Asian Press Alliance said it feared the arrests of Zulkifli and Chia were an attempt to "retaliate against critical voices in the alternative media" and curb the flow of free ideas.

The US-based Committee to Protect Journalists said the arrests of the two were "yet another assault on the fundamental principles of press freedom."

In a letter to Mahathir, its executive director Ann Cooper said their prosecution would send "a message of intolerance that would surely chill the climate for independent journalism in Malaysia."