Seoul: The main opposition Democratic Party (DP) expressed "strong regret" Tuesday over China's recent installation of a steel structure in its overlapping waters with South Korea in the Yellow Sea. "We had expected the Chinese government to take responsible action, but it appears to have no intention of doing so," DP spokesperson Park Kyung-mee said in a written briefing.

According to Yonhap News Agency, Park asked China to immediately halt the construction of any structures that could "damage the trust" built between the two countries and to cooperate with Seoul's investigation. "We strongly urge the Chinese government to refrain from any action that can provoke anti-China sentiment among our citizens, especially at such a sensitive time," she added.

In a Facebook post, Rep. Kim Byung-joo also stressed the DP will "not stand idly by," saying the recent tensions could escalate into a "serious" security issue. "The National Assembly will work to unveil the facts and, if necessary, seek an on-site inspection," he wrote.

The two countries faced a two-hour standoff last month after Chinese authorities blocked Seoul's attempt to investigate Beijing's authorized construction of a steel structure in the Provisional Maritime Zone (PMZ) near Ieodo Island, off South Korea's southwest coast.

The PMZ is an area where the Exclusive Economic Zones of South Korea and China overlap. The two sides have reached an agreement to allow their fishing vessels to operate there and jointly manage marine resources, while prohibiting any activities beyond navigation and fishing.

Despite the agreement, China has installed several large steel structures in the zone, including two in April and May of last year, and another earlier this year, raising concerns over potential territorial disputes.