North Korea's leader Kim Jong Un is believed to have wrapped up an unprecedented whirlwind trip to the Chinese capital, ahead of a planned summit with his South Korean counterpart and a potential meeting with US President Donald Trump.
An official with deep knowledge of North Korea told CNN Tuesday there was a "strong possibility" that Kim was in Beijing after speculation began swirling late Monday about the arrival of a high-level North Korean official.
The rumors started after images were shared online of what appeared to be a train that belongs to North Korea's ruling Kim family arriving in Beijing, and intensified as security officials closed roads outside the Diaoyutai State Guesthouse, where North Korean leaders have previously stayed.
Analysts said the visit was likely aimed at shoring up Pyongyang's relationship with China, its traditional ally and economic benefactor, after a diplomatic thaw that took many observers by surprise earlier this year.
If Kim did make the journey from Pyongyang to the Chinese capital, it would be the first time the young leader has left his home country since taking power after his father's death in 2011.
When asked Tuesday if the North Korean leader was in Beijing, Hua Chunying, a spokeswoman for China's Foreign Ministry, said she had "no idea."
A CNN team saw a motorcade arriving at Beijing Station on Tuesday afternoon and Japan's Kyodo news agency reported that the distinctive green, armored train had left the Chinese capital, presumably bound for Pyongyang.
The unannounced visit followed a flurry of diplomacy that saw North Korea's participation in the Winter Olympics in Pyeongchang last month.
The thawing of relations soon led to the bombshell announcements that Kim would meet South Korean President Moon Jae-in in April, and that Trump had accepted an offer to meet Kim.
South Korean officials who visited Pyongyang as part of diplomatic preparations earlier this month had implored Kim to meet with Trump, the source close to North Korea told CNN Tuesday.
Kim verbally agreed, but didn't think it would be publicized or happen so soon. He was even more surprised that the United States and South Korea made a big announcement regarding a meeting between the two leaders, the source said.
Trump said that the unprecedented meeting with Kim would take place by May , although a spokesman said Monday that the White House was "looking forward to a potential summit some months in advance."
Ties with China
North Korea's relations with China, a traditional ally, have been strained since Kim purged several top-ranking officials close to Beijing, including his uncle, Jang Song Thaek. Tensions were heightened in 2017 after a string of missile tests, which rankled China's leaders and resulted in multiple rounds of United Nations sanctions targeting North Korea's ability to bring in cash.
Experts have noted that while China has publicly lauded peaceful efforts to resolve tensions on the Korean Peninsula, it may have feared being relegated to the sidelines in developments that could shake up regional geopolitics.
Tong Zhao, a North Korea expert at the Carnegie Tsinghua Center for Global Policy in Beijing, said the visit may have been geared toward enlisting China's support ahead of Kim's proposed summit with Trump, and as a back-up plan should diplomatic talks fail.
"North Korea wants to have some insurance against this upcoming summit meeting with President Trump ... the meeting is very important but also very risky," he said. "If the meeting fails, the US could declare that diplomacy has failed and shift to a more coercive approach or even a military strike."
China has a mutual defense treaty with North Korea under which both parties pledge to "immediately render military and other assistance by all means at its disposal" in the event of war or foreign attack, though some analysts have called into question whether Beijing would honor it.
In the absence of official confirmation of Kim's visit to Beijing, analysts speculated that another high-ranking official could have made the trip.
"I think we are left either with the possibility of it being Kim Jong Un or Kim Yo Jong," Michael Madden, an expert in North Korean leadership said earlier Tuesday,
Kim Yo Jong is Kim's sister and the head of the Korean Workers' Party's Propaganda and Agitation department.
Kim Yo Jong last left North Korea to attend the Winter Games in Pyeongchang in February, when she twice shook hands with South Korea's Moon, and passed him a personal invitation to visit Pyongyang. The approach led to plans for a summit between Moon and Kim.
"Numerous other senior officials could and would have taken a private plane, possibly departing without any fanfare in Pyongyang and arranging to establish an unobtrusive arrival with the Chinese authorities," Madden said.
Both Kim Jong Il and Kim Il Sung, the current leader's father and grandfather respectively, traveled by heavily armored train when they visited their allies in China and Russia.
The South Korean government also said it couldn't confirm whether the North Korean leader was in Beijing. If he was, Moon's administration said it would be positive sign that shows ties between Pyongyang and Beijing are improving, a senior official with the Blue House -- South Korea's equivalent of the White House -- told reporters.
Raj Shah, a spokesman for the White House, said he could not confirm the reports of Kim visiting Beijing when asked about them Monday. "We don't know if they're necessarily true," he said.