Malaysian police have arrested 10 people for "acts of terrorism", saying they were members of an international terror organisation and a threat to national security.

The country's home minister confirmed that the arrests were made under the Internal Security Act (ISA), the British colonial-era law which allows for indefinite detention without trial.

Hishamuddin Hussein said in Kuala Lumpur on Wednesday the detainees included nine foreigners, most of whom had arrived in Malaysia recently and were believed to have links to an international terrorist organisation.

"This is a very serious threat to the security of our country," he said.

"We have worked with international intelligence organisations in this operation," he said.

Hussein said all 10 were involved in international terrorism.

He did not reveal their nationalities, or whether they had planned or carried out any attacks.

Hishamuddin said that "if they are with an international terror organisation and if they are caught in Malaysia, then we will take action on them".

'Go to trial'

Rights activists condemned the new detentions and said that suspects should face the normal justice system.

"We oppose the new arrests. We are against detention without trial and the use of ISA on these 10 individuals. We want the government to charge or release them," Nalini Elumalai, co-ordinator of the Abolish ISA Movement, told the AFP news agency.

"If the government has evidence that they pose a threat to national security, please bring them to court and put them through an open trial, don't use ISA on Malaysian citizen or any other individuals."

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

Malaysian authorities reportedly detained 50 people under the law last week although most of them were subsequently released, according to the advocacy movement, which said that 12 others were still in detention.

The detentions come at a time of raised religious and ethnic tensions over the use of the word "Allah" by Christians to denote their God in Malay language publications.

The government had threatened to use the ISA to keep tensions from boiling over.