Former North Korean leader Kim Jong-il's widow appears to have been purged by the Kim Jong-un regime, the U.S.-based Radio Free Asia said Tuesday, citing multiple sources familiar with the reclusive country.

A Chinese businessman, fresh from his recent visit to Pyongyang, told the RFA that Kim Ok, 52, the fourth wife of the deceased leader, was sent to a political prison camp within a year of her step-son taking power. The incumbent leader inherited the country following the sudden death of his father Kim Jong-il in late 2011.

The businessman said he heard from a senior official of the North's ruling Workers' Party that, as well as Kim Ok, others related to her were also sent off to labor camps.

The RFA reported in 2013 that Kim Ok's father Kim Hyo, then a senior official in the Workers' Party's Finance and Accounting Department, was dismissed from his post.

The latest report said members of Kim Ok's family, including her younger brother Kim Kyun, who had been cited for opulence and behaved haughtily thanks to his sister's standing, were all incarcerated, according to the RFA.

"Kim Kyun acted high-handedly and tyrannically as his sister was Kim Jong-il's favorite, after Kim Jong-un's real mother Ko Yong-hui died in 2004," the source told the RFA.

Kim Kyun was appointed the first vice president of the North's prestigious Kim Il-sung University in February 2011 but abruptly resigned from the post in October 2013.

Another source also said that Kim Ok was removed from power as Kim Jong-un moved to tighten his own grip over the country.

The insider said that unless Kim Ok was removed, the North's scheme to idolize Kim Jong-un's biological mother, Ko Yong-hui, would have run into hurdles.

Right after he took power, Kim Jong-un attempted to purge the powerful military elite from the Kim Jong-il era, getting rid of key people in the military, party and government.

Kim Ok, meanwhile, reportedly studied piano at the Pyongyang University of Music and Dance, and became a secretary to the senior Kim in 1980. (Yonhap)