The government warned it would apply a draconian law which allowed for detention without trial to people who used text messages to spread libelous or false information.

The move comes after text messages with rumours that ethnic Muslim Malays would be baptised as Christians sparked a large Muslim protest in Perak.

Deputy Internal Security Minister Johari Bahrum said Internal Security Act (ISA) could be used on anyone spreading texts which could cause instability in the country.

"What happened in Perak was very serious and could have triggered a riot," Johari was quoted as saying in the New Straits Times .

"The SMS caused a lot of uneasiness among the Muslim community, and this is not good for the security of the country, which has various races and religions," he said.

The ISA allows for two-year detention periods that can be renewed indefinitely. It has been used on alleged Islamist militants, but rights groups also say it is a tool to silence government critics.

A thorny matter

Inspector General of Police Musa Hassan said the ISA would be appropriate for those deemed a threat to public order and national security.

"We can conduct investigations under the ISA if the matter becomes serious," he was quoted as saying in the Sun newspaper.

About 1,000 Malays protested outside a Roman Catholic church Sunday in Perak, after some received text messages which said there would be a baptism ceremony involving Muslims.

They later found out the baptism was for some 100 ethnic Indians who had converted to Christianity, according to reports.

Religious conversion is a thorny subject in majority-Muslim Malaysia, where Muslims are not allowed to convert, and proselytising of Muslims by other faiths is also prohibited.

Race relations in the multicultural nation have become increasingly strained recently amid a campaign for religious freedom by activists and a series of controversial court cases.

Prime Minister Abdullah Ahmad Badawi in July ordered a halt to public discussions and threatened penalties against anyone who inflamed emotions.