At a news conference on Thursday a rights group said that the 10 include four men from Syria, two from Nigeria and one each from Yemen and Jordan.

Witness account

Syed Ibrahim Syed Noh, the head of the Abolish ISA Movement that assists people held under the ISA, told reporters the men were among 50 people arrested last week.

"The detentions may have been initiated in response to international pressure on terrorist threats in Malaysia ... but nothing can be confirmed," he said, urging the government to either charge the men in court or release them.

"They [police] asked what were our plans, what did he [Aiman] teach us"

Muhammad Yunus Zainal Abidin, a witness to last week's arrests

Muhammad Yunus Zainal Abidin, who witnessed last week's arrests, identified one of the detainees as Aiman al-Dakkak, a 50-year-old Syrian freelance religious teacher who has been living in Malaysia since 2003.

Muhammad Yunus said he was with about 50 men at a religious talk by Aiman on January 21 at his home on the outskirts of the Malaysian capital, Kuala Lumpur, when police stormed the house.

He said the police, wearing bullet-proof vests and armed with machine guns, took all the men to a police training centre in the city.

Muhammad Yunus said most of them at the talk were international students aged between 20 and 40, and comprising Malaysians, Nigerians, Eritreans, Syrians, Jordanians, a Saudi Arabian and an American.

He said police wanted to know if anyone in the group was from Yemen, Russia or Pakistan, and later separated them by nationalities for questioning.

"They asked what were our plans, what did he [Aiman] teach us," he said, adding that all of them were later released, except for a dozen men including Aiman.

'Wake-up call'

Hishammuddin Hussein, the Malaysian home minister, did not give details on the arrests saying it may jeopardise the investigations.

He said the detainees posed a "serious threat" to security and that their arrests were based on co-operation with foreign intelligence agencies.

"This is a very good wake-up call for us because the playground for terrorists is no longer just one nation. The whole world is their playground," he added.

The ISA, a legacy of the British colonial-era, allows for indefinite detention without trial.

The controversial law has in the past been used against suspected anti-government fighters, including members of Jemaah Islamiyah, a Southeast Asian group believed to be linked to al-Qaeda.