South Korea's spy agency has verified former North Korean Foreign Minister Ri Yong-ho was purged, but it remains unclear whether he was executed.

The National Intelligence Service(NIS) gave the confirmation on Thursday during a plenary session of the parliamentary intelligence committee.

The confirmation came a day after Japan's Yomiuri Shimbun daily reported that Ri appeared to have been executed last year, citing sources familiar with North Korean affairs. 

The report said that four or five officials from the North Korean foreign ministry appear to have been executed one after the other around the time of Ri's execution. 

Yomiuri said that multiple figures, including Ri, had worked in the North Korean Embassy in Britain, and some issues related to the embassy might have been the reasons behind their executions.