Image copyright AFP PHOTO / KCNA VIA KNS Image caption Mr Kim was pictured in state media speaking to an injured Chinese tourist

North Korean leader Kim Jong-un has expressed "bitter sorrow" over a bus accident that left 32 Chinese tourists and four North Koreans dead.

The accident took place on Sunday night in North Hwanghae province, when the tour bus plunged off a bridge.

It is rare for North Korea's tightly-controlled media to report on negative news, and for Mr Kim to acknowledge the incident itself is even more unusual.

China is the North's main political ally and largest trading partner.

"[Mr Kim] said that the unexpected accident brought bitter sorrow to his heart," the official KCNA news agency reported.

"He couldn't control his grief at the thought of the bereaved families who lost their blood relatives."

Image copyright AFP PHOTO/KCNA VIA KNS Image caption Mr Kim expressed his 'sorrow' to Chinese ambassador Li Jinjun (2nd R)

The North Korean leader was pictured visiting injured passengers in hospital. The report said he "personally learned about the treatment".

He also visited the Chinese embassy in Pyongyang, where he met the Chinese ambassador to North Korea Li Jinjun and "expressed his heartfelt condolences and sympathy."

China and North Korea have been long-time allies. Mr Kim's rapid visit to the injured people - and the reporting of it - is likely to be seen in part as a way of protecting his image among the Chinese population.

Chinese tourists make up an estimated 80% of foreign tourists to North Korea - providing an important source of currency for Pyongyang.

Mr Kim earlier this year visited Chinese President Xi Jinping in Beijing, his first known foreign trip since he took office in 2011.

China is responsible for virtually all of North Korea's food and fuel aid and by many measures, can be considered its most important partner.

North Korea recently announced it was halting all nuclear and missile tests, as it builds up to major summit with the leaders of South Korea and the US.