BEIJING (AP) — Japanese and South Korean media were speculating Tuesday that a high-ranking North Korean official had visited China after an airliner from the North landed in the Chinese port city of Dalian.

South Korea's Yonhap News Agency reported that North Korean leader Kim Jong Un may have been aboard the plane. Kim visited China in March for the first time since taking power six years ago, a trip that was not publicly confirmed by the sides until after he had returned to North Korea by armored train.

Yonhap said the plane arrived Monday amid tight security. Japanese broadcaster NHK ran a picture of the Air Koryo plane that it said had been taken Tuesday afternoon at Dalian's airport.

Japan's Kyodo News agency reported that the plane departed from Dalian later Tuesday.

While there are no regularly scheduled flights between North Korea and Dalian, North Koreans are frequent visitors to the city and its port has been instrumental in two-way trade.

China is North Korea's only major ally, although trade between the countries has fallen off by around 90 percent as Beijing enforces United Nations economic sanctions in response to the North's nuclear bomb and ballistic missile tests.

Chinese Foreign Ministry spokesman Geng Shuang told reporters Tuesday that he had "no information to offer at this moment."

"China and North Korea are close neighbors and always maintain normal communication and exchanges with each other," Geng said.