South Korean opposition lawmakers have ignored President Park Geun-hye to visit China in a bid to discuss the planned deployment of an advanced US missile system to the Korean Peninsula.

The group of lawmakers from the main opposition Minjoo Party left the country on Monday for Beijing in an effort to calm the situation.

Relations have become tense after the US and South Korea made a final decision last month to deploy the Terminal High Altitude Area Defense (THAAD) missile system in the South Korean territory. 

"We are visiting with the hope of offering at least a little warmth to the icy Seoul-Beijing ties," said Kim Young-ho, one of the lawmakers.

In visiting Beijing, the lawmakers defied the president who had called on them to cancel their trip. Park had said the visit would boost China's opposition to the deployment and deepen divisions inside South Korea.

Inside the country, the government of President Park has faced massive protests since July 13. The residents of Seongju County, which has been chosen for the site of the deployment, argue that the missiles would pose health and environmental risks.

On Thursday, the residents pledged to boycott the deployment in their hometown, describing it as totally "useless" to defending their country.

Park has discarded the concerns of opponents to the deployment, describing them as “ridiculous.” She has also denounced China for expressing concern over the planned deployment, saying Beijing “should raise [concerns] with the North."

Washington and Seoul claim the system will only be used in confronting what they call North Korean threats. China, however, considers the deployment as a threat to its security and has called on Seoul to “think twice” about its decision.

On Wednesday, China’s People’s Daily accused Park of “undermining regional stability and flagrantly damaging the security interests of neighboring powers,” through the deployment.

THAAD, which is planned to be installed by the end of next year, has been designed to intercept ballistic missiles inside or just outside the atmosphere during their final phase of flight.