China has lodged stern representations with the Republic of Korea after it deployed the remaining launchers of an advanced US anti-missile system, a Foreign Ministry spokesman said on Thursday.

"We, again, urge the United States and the ROK to value the security interests and concerns of China and other regional countries, to immediately halt the deployment process and withdraw related equipment," ministry spokesman Geng Shuang said at a daily news conference in Beijing.

Earlier on Thursday, four mobile launchers and other elements, such as a power generator, of the Terminal High Altitude Area Defense missile interception system were transported to Seongju, some 217 km south of Seoul, by US trucks, according to Xinhua News Agency.

With the additional deployment and construction work, the THAAD battery, which will be operated by US Forces Korea, will be fully operational, Xinhua said.

"China's opposition to the US deployment of THAAD in the ROK is firm, clear and consistent," Geng said. "China has lodged stern representations with the ROK over this."

Seoul and Washington announced the plan to install THAAD in the ROK in July 2016 and started deployment despite strong opposition from Beijing and Moscow on a number of occasions.

The system's radar can peer deep into Chinese and Russian territories although Washington and Seoul claim its usage "will be focused on threats from Pyongyang".

On Monday, Russian Deputy Foreign Minister Sergey Ryabkov said that Russia may be forced to take military measures to counterbalance the THAAD deployment, Russia's TASS news agency reported.

Da Zhigang, director of the Institute of Northeast Asian Studies at the Heilongjiang Academy of Social Sciences, said the deployment of THAAD threatens China's core security interests and is a key factor in the stalemate in China-ROK relations.

"China and Russia need more deterrent countermeasures and communication skills to contain the deployment process more effectively," he said.

Zhou Jin contributed to this story.

mojingxi@chinadaily.com.cn