North Korean leader Kim Jong-un has sent a special envoy to Beijing amid cooling relations between the neighbouring nations.
Choe Ryong-hae, a top military official, flew to the Chinese capital on Wednesday, state media KCNA reported.
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, the BBC reports.
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.
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.
However, in recent weeks, following Pyongyang's nuclear test on 12 February 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.