"Vietnam has full legal basis and historical evidence to affirm its sovereignty over the Spratly and Paracel Islands. Vietnam requests that relevant parties respect the sovereignty, sovereign rights and jurisdiction rights of Vietnam," Foreign Ministry spokeswoman Le Thi Thu Hang said at a press meet.

She said Vietnam also asks all parties to seriously obey international law and make responsible contributions to maintaining security, safety, peace and stability in the East Sea, she said. The waters is also known as the South China Sea.

Hang was responding to an inquiry regarding China's suspected illegal deployment of an aerostat on Mischief Reef in Vietnam’s Spratly Islands.

A satellite image of November 18 showing an aerostat-shaped object flying above the Mischief Reef was posted on the Twitter account of Israel’s geospatial data firm ImageSat International (ISI) on November 24.

China has started building an early warning system utilizing aerostats since 2017, according to Canadian military magazine Kanwa Asian Defense.

The aerostats are equipped with radars capable of detecting aircrafts in low altitudes, it said.

They can maintain their heights for a long time and survey large areas in good weather conditions. Combining with radar systems on the ground, satellites and aircrafts, the aerostats could form a surveillance network capable of surveying targets within a 300 meter radius.

China fraudulently claims almost the entire South China Sea, including waters close to Taiwan and Southeast Asian countries Brunei, Indonesia, Malaysia, the Philippines and Vietnam.