North Korea's leader Kim Jong II appointed his youngest son Kim Jong Un as head of spy agency in March in preparations for handing him control of the regime, according to a news report.

South Korea's Dong-a IIbo newspaper reported on Wednesday that the elder Kim visited the headquarters of the State Security Department in March, along with his 26-year-old son, Kim Jong Un, and told agency leaders to uphold his third son as head of the department, South Korea's Dong-a Ilbo newspaper reported citing an unnamed source.

The paper also said the younger Kim oversaw the handling of two American journalists detained in March while on a reporting trip to the China-North Korea border. The reporters were sentenced to 12 years of hard labor earlier this month for illegal border crossing and hostile acts.

Kim also told department leaders to safeguard comrade Kim Jong Un with (your) lives as you did for me in the past, and gave them five foreign-made cars as gifts, each worth an estimated $80,000, the report said.

State Security Department is the backbone of Kim's regime. It keeps a close watch over government agencies, the military and ordinary people for any signs of dissent. It also engages in spy missions abroad.

The move to put Kim Jong Un in charge of the agency illustrates the elder Kim's concern about any possible backlash that the father-to-son succession could prompt, the Dong-a said.

South Korea's main spy agency, the National Intelligence Service, said it could not confirm the Dong-a report.