BANGKOK, Thailand — One of Burma’s most notorious rebel leaders surrendered to the authorities yesterday, providing a propaganda coup for the country’s military dictatorship.

Johnny Htoo, who with his cheroot-smoking twin brother, Luther, led an ethnic minority militia when they were both still children, turned himself in along with eight followers at a Burmese military post, handing over a collection of weapons.

Now believed to be 18, he had been living with his brother and their parents at a refugee camp in Thailand after surrendering to authorities there in 2001. His motive for returning to Burma was unclear last night.

Burma’s Myanma Ahlin newspaper said Mr. Htoo had “returned to the legal fold.” The group handed itself over as it did not want to be “bullied by other insurgent groups” and wanted to “take part in regional development tasks and live peacefully with their families and relatives.”

There was no mention of Luther Htoo in official reports, although the dissident Democratic Voice of Burma radio said he had taken similar action.

The twins attracted international attention five years ago when reports emerged of two children from the Karen ethnic group leading a Christian militia called God’s Army.

According to the myths that were built around them, at the age of 9 they repelled a Burmese army assault on their village and then assembled a band of rebels. Their black tongues were taken as a sign of divine protection, and they were believed to be immune to bullets and land mines, having been sent to save their people.

But they fell from grace after members of their unit and an allied group, the Vigorous Burmese Student Warriors, seized Ratchaburi hospital in Thailand, holding hundreds of people hostage until 10 guerrillas were killed in a Thai commando assault. In recent years God’s Army has been effectively defunct.

The twins were last heard from two years ago, when it emerged that Luther Htoo had married in the camp and had fathered a boy. Both were said to have swapped their AK–47s for musical instruments.

At the time, Johnny Htoo said: “The difference between taking up arms and holding a guitar is that when you hold arms you are a warrior ready to die for your nation, but with a guitar you feel good.”

The news came as Burma, which has been under military rule since 1962, was heavily criticized at a regional forum.

While the official communique from the Association of Southeast Asian Nations foreign ministers meeting in Kuala Lumpur replicated the anodyne calls for progress of previous years, Malaysia’s foreign minister, Syed Hamid Albar, said: “We have sent a very strong message. We are not happy with the pace of democratization. We want those under detention to be released.”

Activists welcomed the shift in attitude, which they said reflected the failure of Asean’s efforts to engage Burma since it joined the group nine years ago. “It was the most scathing expression of frustration from Asean, reading the riot act to the military regime,” said Debbie Stothard of the pressure group Altsean-Burma.