SEOUL/BEIJING -- The mystery North Korean official who arrived in Beijing on Monday was indeed leader Kim Jong Un, and he met with Chinese President Xi Jinping, sources familiar with the matter said.

Xi and Kim, if the visitor was him, are thought to have discussed mending the bilateral ties frayed by North Korea's pursuit of nuclear weapons. Other key Chinese figures including Vice President Wang Qishan and senior diplomat Yang Jiechi, a member of the Communist Party's Politburo, also attended the Tuesday meeting, sources said.

This would be Kim's first time abroad since he became North Korea's leader in December 2011 following the death of his father. He has not met with Chinese leaders publicly in his own country since October 2015, when Liu Yunshan, then a member of the Politburo, visited the North.

Roads near the Diaoyutai State Guesthouse in Beijing were blocked off for a motorcade Tuesday morning. The motorcade -- which drove by at high speed, led by about a dozen police motorcycles -- appeared to be roughly the same size as the one in which U.S. President Donald Trump traveled on his visit to China in November.

This suggests the mystery visitor was a head of state or someone of a similar status. Police officers warned onlookers not to take pictures.

A motorcade believed to be carrying North Korean leader Kim Jong Un enters the Beijing Railway Station on March 27. © Kyodo

Some sources say Kim's sister, Kim Yo Jong, accompanied him on the trip. But others say Kim Yo Jong herself was the guest of honor, and that the North Korean leader did not go to China at all. The last North Korean leader to visit China was Kim Jong Un's father, Kim Jong Il, in May 2011.

The North Korean official left Beijing later Tuesday on a special train.

At a scheduled news conference on the same day, Chinese Foreign Ministry spokeswoman Hua Chunying did not confirm that a high-level North Korean official had visited China.

Bilateral relations deteriorated after North Korea conducted its third nuclear test in February 2013 over Chinese objections. Jang Song Thaek, Kim Jong Un's uncle and a key go-between with China, was executed as a traitor the following December. Relations cooled even further in recent years, with North Korean media openly criticizing Beijing and China backing United Nations sanctions on Pyongyang.

Yet observers suspect that China sought the Tuesday meeting, and North Korea accepted, because both stand to benefit from stronger ties.

China has used its access to the North to parry American pressure on economic and trade issues. But Kim is scheduled to meet directly with South Korean President Moon Jae-in at the end of April and with Trump by May, which could diminish China's role in future negotiations. Beijing may be eager to show the world that it wants to remain involved in resolving the crisis on its doorstep.

North Korea continues to face military and economic pressure from the U.S. even after Trump agreed to meet with Kim. A complete break with China likely would weaken the North's position ahead of the encounter with Trump. On the other hand, if Kim refuses to abandon nuclear weapons, better ties with Beijing would give North Korea more wiggle room under what would likely be tighter U.S. pressure.

The motorcade Tuesday also was seen at Zhongguancun, a district in Beijing sometimes called the Silicon Valley of China. Analysts speculate that the North Korean official visited the area as a nod to China's calls for Pyongyang to open up its economy.

"China is willing to make concerted efforts with [North Korea] to stay committed to developing our good-neighborly and friendly relations," the foreign ministry's Hua said.