KUALA LUMPUR—(UPDATE 2) The alleged leader of an Islamic militant group accused of plotting to crash an airliner in Singapore has been arrested in Malaysia after more than a year on the run, authorities said Friday.

Malaysian Home Minister Hishamuddin Hussein confirmed that Mas Selamat bin Kastari, who had escaped from a high-security detention centre in Singapore, was being held under internal security laws.

"Mas Selamat is under our detention and is being investigated right now. He was planning something which allows us to arrest him," Hishamuddin told a press conference, without elaborating on those plans.

"We are becoming an expert on him so hopefully this time he won't escape us, and the Singaporean experience will help," he said of the Indonesian-born militant who has escaped custody several times.

Hishamuddin would not confirm reports in the Singapore media that Mas Selamat was caught on April 1 in the southern state of Johor, which is separated from Singapore by a narrow waterway.

Malaysia usually holds security detainees in a camp in northern Perak state, but the minister would not say where Mas Selamat was being held, or confirm reports that he had remained in Johor since his flight from Singapore.

Mas Selamat is said to be the head of the Singapore cell of Jemaah Islamiyah (JI), an underground group linked to Al-Qaeda and blamed for the 2002 Bali bombing and other bloody attacks in Southeast Asia.

Singapore officials alleged he was part of a plot to hijack an airliner in Bangkok and crash it into Changi airport -- one of Asia's busiest -- in 2001 following the September 11 attacks that year in the United States.

Now 48, he escaped from his high-security detention centre in Singapore on February 27 last year after squeezing through a toilet window that had no bars and climbing over a fence.

His escape triggered a huge manhunt, but a flood of tips from the public, some inspired by a bounty of one million Singapore dollars ($647,520) put up by two local businessmen, turned out to be false alarms.

The affair made the strict city-state an object of ridicule and triggered a sweeping review of security measures.

Mas Selamat had not been formally charged at the time of his escape, and was being held under Singapore's Internal Security Act which -- like the Malaysian equivalent -- allows for detention without trial.

Singapore's Ministry of Home Affairs said Mas Selamat had been captured in a joint operation between Malaysian police and Singapore's Internal Security Department, but gave no further details.

Mas Selamat had earlier fled Singapore in December 2001 following an Internal Security Department operation against Jemaah Islamiyah. He was arrested in Indonesia in 2006 and handed back.

"He is an extremely skilled and dangerous terrorist and the fact that he has been recaptured improves the security situation in Singapore and the region," said John Harrison, a security analyst at Singapore's Nanyang Technological University (NTU).

"This is irrespective of what he may or may not have been able to accomplish during his escape," he told AFP.

Harrison praised Singapore and Malaysian authorities for their cooperation and said they had kept the news under wraps to get more intelligence away from the media glare.

Sidney Jones, an analyst with the International Crisis Group, applauded the arrest, but said it did not erase the threat.

"In some ways the bigger danger will still come from the people at large," she told AFP from Jakarta.

"I think we've got a number of little splinters. I don't think this arrest will change their strategies."

Rohan Gunaratna, a security analyst at the S. Rajaratnam School of International Studies in Singapore, described Mas Selamat's arrest as a "very significant blow to the JI network because JI is trying to revive."

"Mas Selamat is a key icon of the Jemaah Islamiyah organisation, he is one of the most dangerous terrorists in this region, his arrest is a major setback to the JI organization," he told broadcaster Channel NewsAsia.