Security measures increased in China as rumors swirled around the possibility of Kim Jong Un making a surprise appearance in China.

Speculation about a possible visit by a high-ranking North Korean official circulated around the Chinese capital Monday, after Japan’s Kyodo News reported that a special train may have carried Kim through the northeastern border city of Dandong.

Nippon Japanese TV showed footage of a train arriving Monday in Beijing, the train believed to be carrying the North Korean delegation was observed Tuesday leaving Beijing looked similar to one used by Kim’s father, Kim Jong Il, to visit the country shortly before his death in 2011.

Chinese Ministry of Foreign Affairs spokeswoman Hua Chunying told a briefing in Beijing Tuesday that she had no information about any visit by Kim or the train reported to have carried him into the country. She said any relevant information would be released in due course.

The unannounced visit is the latest in a series of diplomatic power plays in Asia as U.S. President Donald Trump’s battle to lower the U.S. trade deficit becomes entangled with his effort to get Kim to give up his nuclear weapons. Chinese President Xi Jinping has found himself preparing for a trade war with Trump even after supporting progressive rounds of United Nations sanctions against the Kim regime.

If this meeting is confirmed, it may actually be more productive than a photo op between Trump and Kim in a few weeks,” said Melissa Hanham, a researcher at the James Martin Center for Nonproliferation Studies, in Monterey, California. 

China doesn’t want war break out on the Korean Peninsula. Any instability could lead to a refugee crisis or potentially U.S. troops on its border.