Tokyo: More than a hundred relations of Jang Song-thaek, who was executed by firing squad on charges of plotting to overthrow the North Korean state, have reportedly been arrested and sent to prison camps.

Security officials are said to have descended on a suburb of Pyongyang, the capital, to round up family members of Jang, who was uncle by marriage to Kim Jong-un, the reclusive state's leader.

North Korean leader Kim Jong-un walks past his uncle, Jang Song-thaek, at a military parade in February last year. Credit:AFP

Although it is common in North Korea for family members of anyone found guilty of a crime also to be punished, the scale of the latest arrests underlines the lengths to which the country's new "Dear Leader" is going to eradicate his former mentor from the nation's history.

"At around 10pm on the night of [December] 13, the day after Jang was executed, armed men from the Ministry of State Security arrived in the Pyongchon area of Pyongyang, where a lot of his relations lived," a source in the North Korean capital told the Daily NK news website, which is run by defectors based in South Korea. "They took away a few hundred people. It was not just his close relations, but distant members of his family too, like relations of his father. In these circumstances, even his relations outside Pyongyang are not safe."