North Korean leader Kim Jong Un traveled to Beijing for talks with Chinese President Xi Jinping, state-run media in both countries reported early Wednesday.
It is believed to be Kim's first foreign trip since he took power in 2011.
There had been speculation that Kim was spotted aboard a train in China's capital on Tuesday.
China's Xinhua news agency did not answer that question, but reported Wednesday that the North Korean dictator had met with Xi.
South Korea's Yonhap news agency also reported that Kim visited China from Sunday to Wednesday along with his wife, Ri Sol Ju. It cited North Korean state-run radio.
Xinhua called it an unofficial visit, adding that Xi held talks with Kim at the Great Hall of the People in Beijing.
China is North Korea’s neighbor and most important ally.
In a statement Tuesday night, White House press secretary Sarah Huckabee Sanders said: "The Chinese government contacted the White House earlier on Tuesday to brief us on Kim Jong Un's visit to Beijing. The briefing included a personal message from President Xi to President Trump."
She added: "The United States remains in close contact with our allies South Korea and Japan. We see this development as further evidence that our campaign of maximum pressure is creating the appropriate atmosphere for dialogue with North Korea."
Kim has repeatedly vowed to destroy South Korea along with the U.S., while Trump has threatened Pyongyang with "fire and fury."
North Korea tested a total of 23 missiles last year, including 15 that were nuclear-capable. The November launch of which appeared to be an intercontinental ballistic missile, or ICBM, flew farther than any of Kim's previous tests. The North claimed it could reach anywhere in the mainland U.S.
Analysts say that based on the current evidence it's hard to prove or debunk North Korea's claim that it can now hit faraway American targets such as New York or Washington.
North Korea has said in public statements that it wants an official end to the Korean War. The conflict was halted by a 1953 armistice but no peace treaty has been signed. It also wants nothing short of full normalization of relations with the U.S. and to be treated with respect and as an equal in the global arena.
The Trump administration has encouraged China to use its influence to rein in Pyongyang. In September, China ordered North Korean-owned businesses to close and imposed limits on oil to North Korea.
The Beijing visit also comes ahead of a planned meeting with Trump.
The United Nations also imposed tough new sanctions on North Korea last year. On Tuesday, State Department spokeswoman Heather Nauert said Russia and China can "do more" on North Korea.
Former deputy and acting CIA director John McLaughlin said on MSNBC earlier Tuesday that the reported visit highlights China’s nervousness about talks between South and North Korea, and not wanting to be left on the sidelines.
"Anytime the North and South are getting together, it makes Beijing nervous if they’re not in the room."
"I've seen the Chinese attitude on this — that is, North Korean behavior and nuclear weapons — evolve from denial in the early part of the last decade, through recognition to concern today," said McLaughlin, who is also an MSNBC national security analyst.
"I don't think they have control over Kim Jong Un," McLaughlin said. "And having just been in South Korea, and having talked to the South Koreans and having seen the gleam in their eye about the idea of meeting face-to-face with the North Korean leader — not that they’re naïve about it, but they want to talk."
He added: "I think anytime the North and South are getting together, it makes Beijing nervous if they’re not in the room and they don’t have control over it."
McLaughlin said while Beijing wants negotiations to occur "they’d like to have some influence on those talks."
South Korean lawmaker Shin Dong Uk, who is in a minority party and has been critical of South Korean President Moon Jae-in, said on Twitter that Moon and Trump have been tricked again. Borrowing a popular proverb, he wrote in Korean: "Fool me once, shame on you; fool me twice, shame on me."
Gi-Wook Shin, director of Stanford’s Walter H. Shorenstein Asia-Pacific Research Center, said in a phone interview Tuesday night that if Kim wanted to travel secretly, a train seems an odd way to do so.
"Obviously people would notice this special train," Shin said. "In my view it was more like a dramatic gesture — trying to get attention. This was about controlling and maximizing the attention. Let the people speculate, then announce they met in Beijing."
Shin called the talks between Kim and Xi "a positive development."
"China doesn’t want major political change in North Korea," he said. "At the same time they know North Korea maintaining nuclear capacity creates tension."