THE arrival of a mysterious and heavily armoured North Korean train in China has sparked rumours that Kim Jong Un has made a secret visit to the country.

Videos of the train arriving at Beijing train station on Monday under unusually heavy security was circulated by local media.

The train seen in the videos looks similar to the one used by Kim Jong Un’s father, Kim Jong Il, during his 2011 visit to China.

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Japan’s Nippon News Network described the carriage thought to be carrying Kim Jong Un as green with yellow horizontal lines and part of a 21-car train.

A mystery train pulled into Beijing, fueling speculation that it might be carrying North Korean Leader Kim Jong Un. If so, it would be Kim's first trip out of the country since taking power in 2011. @benstracy reporting. https://t.co/hoLGy2g1cY pic.twitter.com/kCD9iSwDB2 — CBS News (@CBSNews) March 26, 2018

Intriguing images from Beijing, captured by Japan's Nippon TV. A 21-car train, similar to one used by Kim Jong Il in 2011, pulled into Beijing Station around 3pm. Met by honor guard and line of VIP cars. Speculation is that Kim Jong Un could be in Beijing. https://t.co/OR40pYEcgG pic.twitter.com/1G5jndciIr — Martyn Williams (@martyn_williams) March 26, 2018

The protective force seen at the station extended to the Diaoyutai State Guesthouse where North Korean leaders have been known to stay on previous visits to China, with a number of police and around 50 vehicles seen in the area.

A spokeswoman for the Chinese Foreign Ministry said she was not aware of the situation and had no further comment.

North Korea’s state-run media had no reports of a delegation travelling to China.

Bloomberg reported that three sources confirmed that Kim Jong Un was travelling on the train in question, but they were unable to be identified because of the sensitive nature of the information that was being given.

If this information is correct, then it will be the North Korean leader’s first known trip to another country since taking power in 2011.

While certain details of the trip are not officially known, Japanese news agency Kyodo has cited sources as saying that the purpose of the visit is to improve ties between Beijing and Pyongyang.

Relations between the two countries have been strained as a result of North Korea’s missile tests and pursuit of nuclear weapons, as well as China’s backing of tough sanctions imposed by the United Nations.

This alleged secret trip comes less than a month after it was announced that Donald Trump had granted an unprecedented meeting to the North Korean leader.

Mr Trump reportedly accepted the invitation almost on the spot, making a unilateral decision and up-ending decades of US foreign policy.

The remarkable meeting will see the two eccentric, headstrong leaders meet as soon as May.