SEOUL (Reuters) - North Korea appeared to have stage a military parade on Thursday - an event that would be closely watched by international observers for signs of new military technology - after wrapping up a rare ruling party congress, Yonhap news agency reported. Pyongyang is under international sanctions for its nuclear weapons and ballistic missile programmes. The parade, which was not shown live on the isolated nation’s state media, began between 6 p.m. and 7 p.m. (0900-1000 GMT) and was still going on as of 8 p.m., Yonhap cited an unnamed South Korean government source as saying. Military aircraft were spotted releasing fireworks in formation, said NK News, a website that monitors North Korea, citing a source who saw fireworks. Ahead of the congress, commercial satellite imagery had shown troops rehearsing in formation and NK News cited a source who said they heard heavy vehicles moving in Pyongyang on Sunday. On Wednesday, Kim Yo Jong, the sister of leader Kim Yong Un and a member of the party Central Committee, criticised South Korea’s military for saying it had detected signs of a parade in Pyongyang on Sunday. The move was an expression of the South’s “hostile approach” towards the North, she said in a statement carried by North Korean news agency KCNA. Leader Kim and other North Korean officials had packed into an indoor stadium in Pyongyang on Wednesday to watch performances from military and civilian art troupes and youth groups, mostly on themes of glorifying Kim’s leadership and reinforcing messaging from the party congress, news agency KCNA reported on Thursday. The congress, which ran for eight days in Pyongyang, was the first since 2016 and just the second since 1980. The performance was the latest in a series of large gatherings this week where Kim and the other attendees did not appear to wear masks or follow other social distancing measures, based on images released by state media. North Korea has not reported any confirmed cases of the coronavirus, but it has imposed strict border closures, domestic travel restrictions and other measures to prevent an outbreak.