North Korean leader Kim Jong-un arrived in China on Monday for a three-day visit at the invitation of Chinese president Xi Jinping, China’s official Xinhua news agency reported on Tuesday.

Kim’s visit, which state media confirmed would last for three days is his fourth summit with Xi, comes amid reports of advanced negotiations for a second summit between the North Korean leader and US president Donald Trump.

Kim, the North’s supreme leader, visited three times last year to pay his respects to the Chinese president, Xi Jinping, after not meeting him for more than six years after his rise to power.

None of the trips were announced in advance, and the earliest indications of the first one – in March, before Kim had met either South Korean president Moon Jae-in or Donald Trump – came when his train was spotted in Beijing.

Denuclearisation talks between the North and the US have stalled, but speculation has mounted of a potential second summit between Kim and Trump.

Harry J Kazianis, director of defense studies at US-based Center for the National Interest said: “Kim is eager to remind the Trump administration that he does have diplomatic and economic options besides what Washington and Seoul can offer.

“In fact, during his New Year’s Days speech, Kim’s ‘new way’ that he referred to may well have been a veiled threat to move closer to Beijing. That should make America quite concerned.”

Speculation that Kim had entered China grew on Monday after a special North Korean train was spotted entering China.

The train crossed the border at about 22.15 local time (14.15 GMT) and was expected in the Chinese capital on Tuesday morning, the South Korean news agency Yonhap reported, citing an informed source.

In the Chinese border city of Dandong, dozens of security vehicles and officials blocked the roads around the station before the train passed through, Yonhap reported, before reopening them afterwards.

-Agencies