A close adviser to Japanese Prime Minister Shinzo Abe arrived unannounced in Pyongyang on Tuesday, raising speculation of a thaw in relations between North Korea and Japan following weeks of warlike threats from the isolated regime.

North Korean state television showed Isao Iijima arriving in Pyongyang and being met by Kim Chol-ho, vice director of the North’s Foreign Ministry’s Asian Affairs Department.

The purpose of Iijima’s visit was not immediately known while representatives of the prime minister’s office and foreign ministry in Japan said they weren’t aware of the top aide’s trip or intentions, Wall Street Journal reports.

The meeting have also taken Washington by surprise. The US State Department’s special representative for North Korea, Glyn Davies, said he had not been informed of the trip and would “discuss with the Japanese”, reports AFP.

The trip has quickly prompted speculation that Abe was using a prominent figure to engage talks with the North on the long-standing issue of Japanese abductions by North Korean agents in the 1970s and the 1980s.