President Yoon Suk Yeol attends his impeachment trial at the Constitutional Court in Seoul, Thursday. Joint Press Corps

President Yoon Suk Yeol's controversial and unsubstantiated comments about China during his impeachment trial are sparking concerns about their potential impact on the relationship between Seoul and Beijing. This is particularly significant as Chinese President Xi Jinping is considering a visit to South Korea for the Asia-Pacific Economic Cooperation (APEC) summit in October.

Yoon, who is facing impeachment over his brief declaration of martial law late last year, has argued that China's alleged interference in South Korea's elections played a role in his decision to impose emergency military rule.

The president's claims appear to be tapping into anti-China sentiment among his supporters, some of whom have grown increasingly hostile toward Beijing.

On Friday, police arrested a man in his 40s, believed to be a supporter of Yoon, for attempting to storm into the Chinese Embassy in Seoul. Dressed as famous comic book character Captain America, the man claimed he was trying to deliver an "anti-China message" to the embassy.

"We express our concern and regret over this incident. We have conveyed these concerns to the Korean government," the embassy said in a statement.

In recent weeks, dozens of protesters have gathered outside the embassy in Seoul, staging what they call a "Festival to Exterminate Communism," chanting slogans such as "Xi Jinping out."

These protests were fueled by claims made by Yoon and his legal team.

In multiple court documents and public statements, the president argued that the National Election Commission's network system was vulnerable to cyberattacks. He suggested that the Chinese government, accused of political manipulation in other countries, could have exploited these vulnerabilities.

Yoon's legal team also alleged that the opposition parties in Korea "are trying to turn this country into a colony of China and North Korea," in a written statement submitted to the court on Jan. 14.

In a letter to his supporters on Jan. 15, the president expressed solidarity with young people opposing what he called a "pro-China" stance, saying, "It was touching to hear the younger generation's opposition toward pro-China forces."

Some conservative lawmakers backing the embattled president have suggested that China may be behind what they describe as an "impeachment maneuver," claiming that Chinese residents are playing a significant role in pro-impeachment protests.

Chinese Ambassador to Korea Dai Bing refuted these claims on Feb. 10, saying, "China has consistently adhered to the principle of noninterference in internal affairs. We believe that the Korean people have the wisdom and ability to handle domestic issues well."

The Chinese Embassy reportedly delivered similar concerns to the government through diplomatic channels.

National Assembly Speaker Woo Won-shik, left, meets with Chinese President Xi Jinping at the Taiyangdao Hotel in Harbin, Feb. 7. Yonhap

These developments are proving to be a major headache for South Korean officials working to stabilize relations with China.

Relations with Beijing had been strained in recent years amid China's dissatisfaction with Korea's growing security ties with the U.S. However, with U.S. President Donald Trump adopting a hawkish stance on China, Beijing has been hinting at wanting to improve relations with its Asian neighbor.

In a recent meeting with National Assembly Speaker Woo Won-shik in Harbin, Xi said he was "seriously considering" attending the APEC summit in Gyeongju, North Gyeongsang Province. If realized, it would mark the first visit by a Chinese leader to Korea in more than a decade, following Xi's last trip in 2014.

The foreign ministry is treading carefully to avoid upsetting the positive mood.

"We cannot comment on statements made during the Constitutional Court's impeachment proceedings," a ministry official said. "But we are in close communication with China to ensure that certain claims do not negatively impact bilateral relations."

During an impeachment trial last Tuesday, National Security Adviser Shin Won-sik, testifying as a witness, declined to answer when Yoon's lawyers asked whether China could be interfering in Korea's elections.

"Since this is based on a hypothetical assumption, I will not answer as it could affect our diplomacy," Shin said.