One of the men most wanted over a failed separatist uprising in southern Thailand in April that left 113 people dead has been arrested by Malaysian officials, a Thai security source said today.

Poh Su Ismail, high on a list of some 30 suspects compiled by the Thais, was arrested in the northern Malaysian state of Kelantan that borders Thailand's revolt-racked, Muslim-majority south.

He was the alleged author of a booklet demanding a separate Islamic state in the south and claiming that mystical powers would protect insurgents from Thai forces.

The booklet was found on the bodies of some of the 108 militants killed on April 28, along with five security forces, on the worst day of separatist fighting that has left hundreds dead this year.

The violence included the storming of a mosque by heavily armed Thai troops killing 32 militants and leading to the resignation of the Thai army commander who ordered the attack.

"We have been informed that the Malaysian authorities have arrested Poh Su Ismail in Kelantan state under Malaysian security laws after they found he was involved with the upheaval on April 28," the security source told AFP .

"The arrested suspect was on the wanted list which Thailand had handed to Malaysia recently," he said.

He said Thailand would not seek his extradition since the suspect was a Malaysian national.

No confirmation

Thai Prime Minister Thaksin Shinawatra confirmed an operation had taken place but said he was still awaiting details.

Malaysia's Deputy Prime Minister and Defence Minister Najib Razak also refused to confirm the arrest.

"I don't want to confirm or deny anything that involves security at this stage," he told reporters, adding, however, that Malaysia was "working closely with the Thais".

The arrest comes days before security officials from both countries were due to gather in Phuket, Thailand, on Sunday for a two-day meeting.

Thai interior ministry spokesman Somchai Phetprasert said the Thais would be asking for an update on attempts to capture suspects believed to have fled to Malaysia.

Thailand's south was plagued by separatist violence until the 1980s when the government managed to curb militant activity, but violence flared again after an attack on an army depot in January.

More than 250 people have been killed and the two nations have pledged to work more closely after frictions when the Thai leadership accused its Muslim neighbour of not doing enough to catch those responsible.

'More enlighted approach'

Najib said he believed the "Thais have realised the way to fight the militants in the south is to adopt a more enlighted approach".

The use of excessive force would be wrong, Najib said, and the solution called for "a more comprehensive package that deals with the legitimate grievances of the people in the south".

The fighting sparked fears of a wider rebellion between rebels in the Muslim-majority south and the overwhelmingly Buddhist population of Thailand.

Meanwhile, a policeman became the latest victim of the southern violence Wednesday when he was shot and killed while travelling to work on his motorcycle in the southern province of Pattani.