China said on Wednesday it had expressed serious concern to Washington and Seoul after the US military started moving parts of its controversial Terminal High Altitude Area Defense (THAAD) anti-missile defense system to a deployment site in the Republic of Korea (ROK).

Speaking at Wednesday’s daily news briefing, Foreign Ministry spokesman Geng Shuang said China has been closely following reports on THAAD and urges the US and the ROK to withdraw the system.

Earlier in the day, trailers carrying the US THAAD missile defense equipment entered a deployment site in the ROK, with tensions high over the DPRK's intentions, the ROK's Yonhap News Agency reported.

The arrival of the six trailers at the golf course location sparked clashes between locals and police, the agency said.

Washington and Seoul say they are deploying the THAAD battery to counter the threat from the DPRK, which is pushing ahead with its ballistic missile program despite multiple sets of UN sanctions.

The THAAD system is meant to intercept and destroy short- and medium-range ballistic missiles during their final phase of flight.

The DPRK is also believed to be preparing for a sixth nuclear weapons test.

Washington and Seoul agreed to the early deployment of the missile defense system after talks earlier this month between the ROK's acting president Hwang Kyo-ahn and visiting US Vice President Mike Pence.

Geng Shuang said the deployment will undermine the strategic balance of the region and cause further tensions on the Korean Peninsula.

“It is not helpful in terms of denuclearization of the peninsula and regional peace and stability," Geng added. "The move hurts the dialogue process and negotiation efforts and will seriously undermine China's strategic security interests. China strongly urges the United States and South Korea to stop actions that harm China's strategic security interests, cancel the deployment of THAAD, and withdraw the equipment.”

The spokesman also said China will "firmly take necessary measures to safeguard its own interests." Beijing has repeatedly expressed opposition to the deployment of the THAAD system.

The coverage of the THAAD missile defense system, especially the monitoring scope of its X-Band radar, goes far beyond the defense needs of the ROK. It will reach deep into the hinterland of Asia, which will not only directly damages China's strategic security interests, but also harms the security interests of other countries in this region, according to the Chinese Foreign Ministry.