Jang Song-taek, the once powerful uncle of North Korean leader Kim Jong-un who was brutally executed in 2013, made two secret visits to Japan, Japan's Kyodo News reported on Wednesday.

Jang entered Japan with a North Korean passport but under a false name in April 1983 and September 1991, presumably to observe the political atmosphere in Japan or receive medical treatment.

In 1983, he pretended to be a senior figure in a performing arts troupe, and in 1991, he posed as a member of a construction-related delegation and received medical treatment near Tokyo.

Jang was married to the younger sister of former North Korean leader Kim Jong-il. After Kim Jong-il died he acted as patron of Kim Jong-un and became one of the most powerful men in North Korea. But internal power struggles led to his downfall and execution in December 2013 on charges of corruption.

He was a leading point man in dealings with China and amassed huge wealth and influence thanks to his Chinese ties, which are vital to North Korea's survival.

