All responsible countries should join hands to defend multilateralism and free trade, Chinese State Councilor and Foreign Minister Wang Yi said, when meeting with Ban Ki-moon, former UN secretary-general and chairman of the Boao Forum for Asia, in Seoul on Thursday.

Wang said the superpower has became a troublemaker in global interactions, violating international rules, ignoring its own international obligations and adopting unilateral and bullying behaviors.

Speaking of China-South Korea relations, Wang said China is willing to work with the other side to deepen cooperation in various fields and advance the bilateral strategic cooperative partnership to a new level.

Ban Ki-moon said he hopes that China and South Korea will have closer cooperation in the future.

"I would like to continue to play a constructive role in promoting South Korea-China relations, tackling climate change and maintaining multilateralism," said the former UN secretary-general.