Thailand has detained six Malaysian soldiers after they mistakenly entered Thai territory during a routine military exercise, officials said Tuesday.

"It was a normal exercise. But they had crossed into our neighbour's border," a Malaysian defence ministry official told AFP.

"The Thais have detained them. But there is nothing to be alarmed about," the official adding that they were expected to be released later Tuesday.

"They are going to release our boys," the official said.

The official Malaysian Bernama news agency said six Malaysian soldiers had crossed into Bukit Tokmok in the troubled southern Thai province of Narathiwat along the border on Monday.

Bernama , citing a Thai military spokesman, said the six were being held at Senanarong Army Camp in Songkhla in Narathiwat for questioning.

Fear prosecution

More than 1,000 people have been killed in Thailand's three Muslim-majority provinces bordering Malaysia since an Islamic insurgency broke out there in January 2004.

A group of 131 Thai Muslims fled across the border last year citing fear of persecution by Thai security forces fighting the insurgency.

The group's flight triggered a diplomatic row between Thailand and mainly Muslim Malaysia, which insisted that they should not be forced to return - particularly if their safety could not be assured.