TOKYO — A political aide to the prime minister of Japan made a sudden, rare visit to North Korea on Tuesday. Japanese officials refused to say what he was doing there.

Japan and North Korea do not have formal diplomatic ties. Talks between the two governments, which resumed last August after a four-year hiatus, were broken off again in December after North Korea tested a rocket.

Kyodo News, a Japanese news agency, reported that the adviser, Isao Iijima, was met at the airport in Pyongyang, the capital, by a North Korean official identified as Kim Chol-ho, a vice director in the Foreign Ministry. Such a reception would suggest that Mr. Iijima, who is a senior adviser to Prime Minister Shinzo Abe, was there on official business.

However, officials in Mr. Abe’s office would not even confirm that Mr. Iijima had gone to Pyongyang, let alone give a reason.