The Chinese Foreign Ministry says the country is building up necessary and proper defence facilities in South China Sea's Nansha Islands, which is a self-defence right given by international laws and a matter within the Chinese sovereignty.

The remark comes after US Deputy Secretary of State, Antony Blinken, said Thursday that China's recent action in the South China Sea is "fuelling regional tension".

"China's building up necessary and proper defence facilities is a self-defence right given by the international laws without any rebuke, It's also a matter within the Chinese sovereignty. China also respects other countries' rights to sail and fly in this region endowed by international laws, but opposes any actions to harm sovereignty and security of countries in the region in the name of free sailing,"

"The US needs to clarify to the world that which freedom it's supporting, freedom under international laws or arbitrary freedom by war ships and planes in the American style," said Hua Chunying, spokesperson of Chinese Foreign Ministry.