Japanese officials have been meeting secretly with North Korea’s ruling party in recent months, according to sources.

The back-channel meetings are an apparent attempt to make progress on pending issues through a different route than the previous dialogue between diplomats.

For at least three meetings between September and November, Pyongyang sent members of the International Department of the Workers’ Party of Korea who are close to leader Kim Jong Un, while Tokyo dispatched Foreign Ministry officials, the sources said Monday.

Japan’s use of the North Korean political party as a conduit may have been primarily aimed at breaking the current stalemate on the abduction issue, the sources said. Tokyo and Pyongyang have no diplomatic ties.

The move is thought to be the first time the party’s department has become directly involved in negotiations with Japan since the summit in 2004 between Prime Minister Junichiro Koizumi and Kim’s father, the late Kim Jong Il.

The sources said the party, which in May held its first congress in 36 years, may be trying to re-establish connections with Prime Minister Shinzo Abe’s ruling Liberal Democratic Party and others in Japan, having finished fully building up a power base under their leader following the death of the elder Kim in late 2011.

According to the sources, officials from both sides held a meeting in an inland city in northeastern China in early September.

The talks continued even after North Korea carried out its fifth nuclear test that month, drawing international condemnation, with contact being made in a port city in southern China in early October and another location at the start of November.

The October meeting was at a higher level than the other two, with Japan represented by a senior Foreign Ministry official with close knowledge of Abe’s intentions and Pyongyang represented by a high-ranking party member able to pass on Kim’s thoughts, the sources said.

The government has denied that Foreign Ministry officials went to China or that contact was made with North Korea.

Japan and North Korea announced in May 2014 that they had reached an accord in Stockholm on principles for negotiations toward the settlement of their outstanding issues, including the abduction of Japanese nationals in the 1970s and 1980s. Japan relaxed its sanctions on North Korea, which in turn promised a full-scale investigation into the abductions.

But North Korea repeatedly postponed reporting the investigation results. After Japan imposed strengthened sanctions last February in reaction to the fourth nuclear test, North Korea disbanded its investigation team and suspended the probe.