un sends envoy to China 22 May 2013 Last updated at 09:10 North Korean leader Kim Jong-un has sent a special envoy to Beijing, state media has announced, amid cooling relations between the two neighbours. Choe Ryong-hae, a top military official, flew to the Chinese capital on Wednesday, KCNA said. The brief dispatch gave no details of the visit, which comes amid an apparent toughening of Beijing's stance in the wake of Pyongyang's third nuclear test. Chinese media said Mr Choe met Wang Jiarui, a top foreign affairs official. The visit - the duration of which remains unknown - follows weeks of high tension on the Korean peninsula. It has traditionally sought to maintain stability in North Korea, avoiding any crisis that could trigger the fall of the regime and propel a flow of refugees across the border. But in recent weeks, following Pyongyang's 12 February nuclear test and amid strident rhetoric from its leaders, China has expressed frustration with North Korea, with state media openly debating the benefits of close ties. Beijing supported expanded UN sanctions against Pyongyang after its nuclear test and some of its banks have recently suspended trading with North Korea's Foreign Trade Bank. It is also under domestic pressure after unidentified North Koreans seized, and subsequently released two weeks later, a 16-strong Chinese crew who had been fishing in the Yellow Sea. Japan talks The KCNA report described Mr Choe as director of the General Political Bureau of the Korean People's Army. He has risen quickly under North Korea's young leader - last year he was promoted to vice-marshal and given senior positions within the party's key organisations, reports the BBC's Lucy Williamson from Seoul. Kim Jong-un inherited the North Korean leadership in December 2011 after the death of his father, Kim Jong-il. The late Mr Kim visited China in August 2011 and his brother-in-law, Jang Song-thaek, who is thought to be a key adviser of the younger Mr Kim, in August 2012. Mr Choe is thought to be the most senior North Korean official to visit China since then. He appears to be the first top-level envoy publicly dispatched by the North Korean leadership to the region since the recent tensions, which saw multiple threats of attacks from North Korea and a show by the US of high-profile military hardware in joint exercises with the South. Japan, meanwhile, said on Wednesday it would be open to direct talks with North Korea if it would help resolve the issue of Japanese nationals kidnapped by the communist state in the 1970s and 1980s. The comments, from Japan's top government spokesman, followed a visit to Pyongyang by a special envoy of Japanese leader Shinzo Abe. South Korea and the US have criticised the visit as unhelpful and said they were not consulted. In another development, a KCNA report named a hard-line general, Kim Kyok-sik, as North Korea's army chief. Mr Kim was previously defence minister, a lower ranked position, until earlier this month. Kim Kyok-sik was said to be responsible for the shelling of South Korea's border island Yeonpyeong in 2010, which killed four South Koreans.