KUALA LUMPUR, April 18 (AFP) - Lawyers seeking the release of Malaysian activists detained under a controversial security law protested Wednesday at a move by the police chief to withhold further information due to "national interest".

As the "habeas corpus" hearing went into its second day in the high court here, government lawyers filed an affidavit from national police chief Norian Mai.

In it Norian states he will not divulge any more information about the detentions, or the reason for them, due to "national interest considerations".

Seven supporters of jailed ex-deputy premier Anwar Ibrahim were arrested last week under the Internal Security Act (ISA), which allows indefinite detention without trial.

The police chief and Prime Minister Mahathir Mohamad have told reporters that Anwar's supporters had plans to use explosives and weapons in street demonstrations to topple the government.

The aim of the arrests was to derail a pro-Anwar protest last Saturday, which passed off peacefully.

Zainur Zakaria, lead counsel for the detainees, told Judge Augustine Paul that accepting Norian's affidavit would "open the floodgates" for more detentions based on unsupported evidence.

"What is there to prevent allegations that the detainees plan to acquire nuclear weapons from Russia to topple the government?" he asked.

Lawyers for five of the detainees have filed habeas corpus writs against Norian, saying their detention was illegal and demanding they be freed.The two others were due to file writs elsewhere.

Habeas corpus is a writ ordering prisoners to be brought before a court or a judge to ascertain whether their detention is lawful.

Zainur has described Norian's allegations as "a pack of lies" and said the detentions are politically motivated.

Five of the seven are members of the opposition National Justice Party, headed by Anwar's wife.

Zainur told the judge Wednesday that the filing of the affidavit was an "improper" attempt to plug loopholes in the government's case.

Paul ruled that he would accept the filing of the affidavit but it was not clear whether he would also accept Norian's unwillingness to give further explanations.

Zainur told the judge: "It is our stand that the arrests are unlawful and the court should order the release of the detainees.

"The Inspector-General of Police (Norian) in his press statement had named seven detainees and cited reasons for their detention, that they were taking steps to obtain grenade launchers and to create chaos around Kuala Lumpur."It's quite clear from the statement that the arrests were due to their (alleged) acts that endanger the security of the country."

Zainur said the court's duty was to "evaluate the allegations and accusations for the grounds of their arrest and detention... at the moment it is our submission that the accusations are without any supporting evidence."

The hearing was continuing.

Anwar, who is serving 15 years in jail after being convicted in separate trials of abuse of power and sodomy, has said he was framed to avert a political challenge to Mahathir. Authorities deny the charge.

Saturday's rally was to mark the second anniversary of Anwar's sentencing for abuse of power. Paul on Tuesday rejected suggestions that he step down from the case since he had been the judge who sentenced Anwar.