China has moved a leading ethnic Mongol dissident to a "luxury resort", a rights group said Thursday, in the first indication of his whereabouts since his jail term ended 17 months ago.

Hada, who like many Mongols goes by one name, completed a 15-year sentence in December 2010 for espionage and separatism after he advocated greater freedoms for China's six million Mongols.

But he was never released and his whereabouts have remained a mystery, although a video emerged online in February last year -- likely released by police -- showing him looking healthy but saying he had not yet gone home.

The Southern Mongolian Human Rights Information Centre (SMHRIC) said Hada had been held in a "secret prison" but had now been transferred to a "luxury resort" in Uuhan Banner, an area in the northern Inner Mongolia region.

The group quoted his uncle as saying Hada was transferred last month.

"I was permitted to have lunch with Hada... on April 20 when he was being transferred to a luxury resort in Uuhan Banner," Haschuluu told the group.

"More than 10 state security personnel escorted him, and two identified themselves as doctor and nurse."

Local police and government were not available for comment.

Police have also harassed Hada's family, amid government concerns of further ethnic unrest in Inner Mongolia after protests hit the region in May and June last year over resource exploitation and Chinese rule.

One of China's longest-jailed prisoners of conscience, Hada was imprisoned in the 1990s after writing essays on greater Mongol autonomy and organising peaceful demonstrations.

Many of China's ethnic Mongols, who have cultural and ethnic ties with Mongolia, complain of political and cultural repression under Chinese rule -- a charge Beijing denies.

According to the overseas-based SMHRIC, Hada is in poor health. His uncle said he suffers from leg pain, back problems, stomach aches and deteriorating vision. He also has kidney problems.

The group said authorities have offered Hada and his family members high paying jobs, expensive cars and luxury houses in exchange for their cooperation and for the dissident to admit his "wrongdoing" -- which he has refused to do.