An aide to Japan's prime minister said Friday he had held "sincere" talks with North Korean officials during his controversial visit to the country.

Isao Iijima, a senior adviser to Japanese Prime Minister Shinzo Abe, was tightlipped about the subjects of his discussions when he arrived at the airport in Beijing Friday.

"By visiting there, I was able to hold sincere talks for a long time," Iijima, a political fixer, told reporters in the Chinese capital, according to Jiji Press.

"I have no plan to grant interviews. I want to closely examine [what was discussed] and consider it," he said.

The Japanese government has refused to discuss Iijima's visit, despite coverage of it by the North's official Korean Central News Agency.

South Korea dubbed the trip "unhelpful" to international efforts to forge a united front against Pyongyang, while the US expressed its surprise and urged Japan to share information.

The North's state media showed footage of Iijima's talks Thursday with Kim Yong-nam, North's Korea's ceremonial head of state, according to Japan's national broadcaster NHK on Friday.

In it, Kim said he appreciated Iijima's work on bilateral relations.

Japanese government ministers, from Prime Minister Abe on down, have refrained from discussing Iijima's visit to the North, including its purpose and the length of his stay.

AFP