Kim Jong-un was rumored to be paying a secret visit to China on Monday after an armoured North Korean train pulled into Beijing under heavy guard. 

Passengers were diverted and services cancelled as the train arrived in Beijing around 3pm, before video emerged showing a car driving away under police escort.

The train bears a marked similarity to one that Kim Jong-un's father, Kim Jong-il, used for his trips to China, sparking speculation that the Supreme Leader was on board.

If the news is confirmed, it would mark Kim's first visit to any foreign country since taking the reins of power.

Japanese news agency Kyodo News reported that a high-ranking North Korean official had arrived in the Chinese capital, but did not say who it was.

The agency said the visit was intended to improve ties between Beijing and Pyongyang that have been frayed by North Korea's pursuit of nuclear weapons and China's backing of sanctions at the United Nations Security Council.

In Beijing, a car with a diplomatic license plate of the North Korean Embassy was spotted at the Great Hall of the People, a state building used for activities by the government and the Communist Party of China, Japan today reports.

Severe traffic regulations were enforced around the city. 

Hotels along the route also suspended reservations in rooms facing the North from Sunday, Japanese sources said. 

The route is the same taken by Kim Jong-il when he visited in 2011, it is reported.