China, an ally of North Korea for decades, is the main source of tourism to the country. Many Chinese tourists visit North Korea seeking a sense of what China was like before it became one of the world’s largest economies. Day trips across the border are popular, as are visits to the North Korean capital, Pyongyang.

Even as tensions over the North’s nuclear program have risen over the past year, the flow of tourists from China has continued. In 2012, the most recent year for which data is available, 237,000 Chinese people visited the country.

Mr. Kim visited the victims of the crash and expressed “bitter sorrow” for the accident, KCNA, the North Korean news agency, said Tuesday. His statement was a rare show of regret by a leadership that typically does not call attention to such negative news inside the country.

The circumstances of the crash, which occurred in North Hwanghae province, near the border with South Korea, remained unclear on Monday, and there was limited coverage in China’s state-run news media. An English-language channel affiliated with China Central Television, the state broadcaster, reported on Twitter that the bus had fallen from a bridge. The post was later deleted.

Chinese state television broadcast images of an overturned blue bus and what appeared to be medical workers tending to injured passengers. The images, taken at night, showed heavy rain.