China appears to be "cynical" about North Korea's behavior amid bilateral tensions caused by Pyongyang's nuclear weapons development, a South Korean diplomatic source familiar with the countries' ties said Wednesday.

"The impression I got was that China's attitude toward North Korea is cynical," the source said, citing bilateral talks between the foreign ministers of South Korea and China earlier in the day.

"I got the feeling that they're displeased with North Korea's behavior."

Foreign Minister Yun Byung-se and his Chinese counterpart, Wang Yi, held talks for 50 minutes on the sidelines of a series of conferences led by the Association of Southeast Asian Nations here this week.

The source, speaking on condition of anonymity, said the impression was based on the way Chinese officials spoke about North Korea.

Once North Korea's closest ally and benefactor, China has recently made clear its annoyance with North Korea's nuclear weapons program.

Chinese President Xi Jinping has yet to visit North Korea, making him the first Chinese president to officially visit South Korea before making an official trip to the North.

Asked whether China appears eager to have North Korean leader Kim Jong-un come to Beijing in September to mark the anniversary of China's victory in World War II, the source added, "They didn't show a willingness to actively push for his attendance."

During their talks, Yun and Wang noted the possibility that the situation on the Korean Peninsula may move in a "very sensitive direction" in the coming months and agreed to strengthen their coordination to prevent a deterioration of the situation, a South Korean Foreign Ministry official said.

North Korea is widely expected to conduct another long-range rocket launch in October to mark the 70th anniversary of the founding of its ruling Workers' Party. (Yonhap)