China on Thursday admitted that it had installed weapon systems on the artificial islands it had built on the disputed South China Sea. However, the country’s Ministry of Foreign Affairs said the deployment was part of normal defence process, and should not be seen as “militarisation”. The ministry said the weapons would be used like a “slingshot” only to deter threats, reported The New York Times.

“If China constructing normal facilities on its own islands and deploying necessary territorial defence facilities counts as ‘militarisation’, then what about sending fleets through the South China Sea?” ministry spokesperson Geng Shuang said. He was referring to the United States Navy’s “freedom of navigation” operation in the region.

The ministry statement posted on its website said the weapons were for “defence and self-protection, and this is proper and legitimate”. “For instance, if someone was at the door of your home, cocky and swaggering, how could it be that you wouldn’t prepare a slingshot?” they said.

After reports of images of the weapons deployed by the Chinese government in the region emerged on Thursday, Senator John McCain, chairman of the Senate Armed Services Committee, said “China is militarising the South China Sea, its leaders continue to lie about that fact, and Beijing is paying little to no price for its behaviour.”

Satellite images captured by Asia Maritime Transparency Initiative showed anti-aircraft and anti-missile systems installed at all seven artificial features created on the sea. “These gun and probable CIWS emplacements show that Beijing is serious about the defence of its artificial islands in case of an armed contingency in the South China Sea,” the US think tank told Reuters.

On Wednesday, Washington had said that it would not stop the operations in the region, even though Beijing called it dangerous meddling. “The US will not allow the shared domains to be closed down unilaterally, no matter how many bases are built on artificial features in the South China Sea,” said Admiral Harry B Harris Jr, head of the United States Pacific Command.

Relations between the US and China have gone from complicated to critical since Donald Trump won the presidential elections on November 9. Trump’s phone conversation with the Taiwanese president further irked Beijing. Taiwan and the US have long severed ties after the rapprochement between Beijing and Washington. The US embassy in Taiwan was also closed down in the 1970s. Taiwan is a democratically-ruled island that Beijing believes to be a breakaway province. However, since the rapprochement, Washington has followed a “one China” principle – according to this, Taiwan is considered a part of the Chinese nation.

Trump has yet to comment on the development on the South China Sea. Several rival countries – China, Philippines, Vietnam, Taiwan, Malaysia and Brunei – have been fighting over this resource-rich territory for years. China has claimed nearly 90% of the territory, which is defined by the nine-dash line, and has also issued a map to back its claims.