China's Defense Ministry has said Beijing will keep a close eye on actions by the US and South Korea over the deployment of the THAAD system.

Ministry spokesperson Yang Yujun reiterated China's stance that it will consider taking necessary steps to safeguard national security and regional balance.

Russia has also raised objections over the use of the anti-missile system. The country's foreign ministry released a statement saying the move would "undermine the established strategic balance in the region". It said the US and South Korea should re-consider actions that could result in irreversible consequences.