South Korea said on Thursday it summoned China's ambassador to protest at Beijing's criticism of South Korean President Yoon Suk Yeol's remarks on Taiwan.
The move came after China and South Korea exchanged harsh words over Yoon's comments in a recent interview with Reuters.
In an exclusive interview with Reuters, Yoon said increased tensions around Taiwan were due to attempts to change the status quo by force, and he opposed such a change.
"The Taiwan issue is not simply an issue between China and Taiwan but, like the issue of North Korea, it is a global issue." Yoon said.
Chinese foreign ministry denounces Yoon
Asked about Yoon's comments, the Chinese foreign ministry denounced Yoon and called on South Korea to "prudently handle matters" related to Taiwan.
"Its resolution (of the Taiwan issue) is a matter for Chinese who do not need to be told what should or should not be done," spokesperson Wang Wenbin told a regular news briefing on Thursday.
Hours later, South Korea's foreign ministry hit back and said comments by the Chinese foreign ministry were "unspeakable."
A vice foreign minister called in Chinese Ambassador to South Korea Xing Haiming and strongly protested what South Korea called "diplomatic discourtesy," the South Korean foreign ministry said in a statement.
On Sino-US rivalry, the South Korean leader has trodden cautiously, with China being South Korea's largest trade partner, but he has been more vocal over tension in the Taiwan Strait.
Tensions over democratically governed Taiwan, which China views as its own territory, have spiked over the past three years as Beijing ramps up diplomatic and military pressure to get Taipei to accept Chinese sovereignty.