North Korean leader Kim Jong-un has sent a special envoy to Beijing, the state media has announced.
A top military official, Choe Ryong-hae, flew to the Chinese capital on Wednesday.
The visit comes amid an apparent toughening of Beijing's stance in the wake of Pyongyang's third nuclear test, reports BBC News.
The visit - the duration of which remains unknown - follows weeks of high tension on the Korean peninsula.
Chinese media said Choe met Wang Jiarui, a top foreign affairs official.
China is North Korea's biggest trading partner and closest ally. 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.
Media reports described Choe as director of the General Political Bureau of the Korean People's Army.
