UN secretary-general Ban Ki-moon said on Sunday that he "really appreciates" China's efforts to invite the largest number of developing countries to attend the G20 summit.

"It's easy to say 'we support developing countries', but it is difficult to really take action to help those people," Ban said, adding that it is in line with the "persistent Chinese efforts" to push forward South-South cooperation.

He made the remarks while attending a news conference during the sidelines of the two-day G20 summit held in Hangzhou which started on Sunday.

"I thank His Excellency Chinese President Xi Jinping and Chinese presidency for emphasizing sustainable development efforts as the core element of the G20 agenda," he said.

Ban told reporters that it's his second time coming to Hangzhou, where the economic and social development is impressive and the people live in peace and stability. "This kind of benefit and opportunity should be shared by people around the world."

Mentioning that it's the last G20 summit meeting he will be attending as UN secretary-general, Ban congratulated China for "successfully hosting and wonderfully organizing" this G20 summit.