North Korea has issued a rare public apology after its border guards killed three Chinese citizens, promising to punish those responsible and to ensure that such incidents do not happen again, the Xinhua news agency reported yesterday.

North Korean authorities said the shootings were an “accident” that was being investigated and extended condolences to the bereaved families, Xinhua said.

The report suggests that the regime in Pyongyang, whose diplomatic style often verges on the truculent, is working hard to try and soothe relations with China, which is its principal political ally and economic backer. So far Beijing has refrained from criticising the North Koreans over the alleged torpedoing of a South Korean warship in March, in which 46 sailors died.