BEIJING, Nov 18 (AFP) - US President Barack Obama left China on Wednesday for South Korea, the final stop on his four-nation Asian tour, an AFP photographer said.

Obama began his visit to China late Sunday in the booming financial centre Shanghai, where he called for expanded political freedoms and an unshackled Internet.

He then held talks in Beijing with President Hu Jintao, Premier Wen Jiabao and other top leaders, in which both sides expressed a willingness to deepen their strategic partnership.

Obama noted on Wednesday that Sino-US ties were "now expanding to deal with a whole host of global issues in which US-China cooperation is critical".