BANGKOK (Reuters) - An exiled Thai opposition activist and outspoken critic of Thailand’s ruling junta has been abducted in Laos, a rights group said on Tuesday, calling on authorities in Thailand and Laos to investigate the disappearance.

Wuthipong Kochathamakun, a member of the “red shirt” movement that has backed populist governments led by former Prime Minister Thaksin Shinawatra, has been in hiding in Laos since 2014, according to Thai authorities.

Wuthipong said earlier this year he was training “civilian warriors” to oust Thailand’s military government.

He was assaulted on Saturday morning in Vientiane, Laos’ capital, by a group of 10 armed men dressed in black, before he was put in a car and driven away, Human Rights Watch said in a statement on Tuesday. His wife and friend, who were also hit and shocked with stun guns, were left at the scene, the group said.

Human Rights Watch said it had interviewed multiple witnesses. Thai media, quoting their own sources, also reported that Wuthipong had been abducted.

Reuters was unable to contact Wuthipong or his wife for comment. Authorities in Laos made no comment.

“Wuthipong’s shocking abduction by armed men in Vientiane needs to be fully investigated; it should not be treated with silence or swept under the rug,” said Brad Adams, Asia director at Human Rights Watch.

Thailand’s military government has denied any knowledge of Wuthipong’s disappearance.

Thailand has been pushing Laos to extradite Wuthipong since October, along with other suspects who live abroad and are accused of insulting the Thai monarchy. The junta accuses him of running a radio channel critical of the monarchy.

In March, Wuthipong was accused by the military government of hiding a cache of weapons in Thailand and plotting to kill Prime Minister Prayuth Chan-ocha. He denied the accusation.

Despite the military government denying any knowledge of his disappearance, Thawip Netniyom, chief of Thailand’s National Security Council, told reporters on Tuesday that Wuthipong could be setting up his own disappearance to damage the junta’s image.

“His disappearance was likely aimed at creating a buzz,” Thawip said. “Such news is designed to affect the government.”

Wuthipong is affiliated with the red shirt United Front for Democracy against Dictatorship group, which supports Thaksin, overthrown in 2006, and his sister Yingluck Shinawatra, who was toppled as prime minister in 2014.

“I can’t say for certain but there is a 60 percent chance that he was kidnapped,” Thanawut Wichaidit, a spokesman for the group, told Reuters. He said it was unlikely that he had set up his own abduction.