A high-ranking North Korean figure appears to be visiting China by train, sources close to the matter said Monday, but it has yet to be confirmed whether it is the country's leader Kim Jong Un.

The tight security in the Chinese border city of Dandong has prompted speculation that an important foreign dignitary is now or has already been in China, the sources said.

Hotels around the Sino-Korean Friendship Bridge linking Dandong with the North Korean town of Sinuiju have not allowed their guests to enter rooms facing the river on Monday afternoon, in an apparent move to prevent the train from being seen, the sources said.

A hotel source said it is rumored that a North Korean dignitary would visit China. Security in Beijing will be strengthened in the early morning on Tuesday, another source said.

A diplomatic source in Beijing told Kyodo News that the figure may be Kim, who in his New Year's address on Jan. 1 voiced readiness to meet with U.S. President Donald Trump again anytime.

Pyongyang is believed to be trying to gain backing from China to promote negotiations with Washington, which have been mired in a stalemate against a backdrop of the Trump administration's skepticism about Kim's intention to give up nuclear weapons.

In March last year, Kim traveled to Beijing in his first foreign trip since becoming North Korea's supreme leader following the death of his father Kim Jong Il in 2011. During 2018, he visited China three times to hold talks with Chinese President Xi Jinping.

At their historic meeting in Singapore on June 12, 2018, Kim and Trump agreed that the United States would provide security guarantees to North Korea in exchange for its "complete denuclearization."

China and North Korea fought together in the 1950-1953 Korean War against the U.S.-led United Nations Command. The two countries have been described as "blood brothers."