BEIJING, Jan. 19 -- China on Tuesday said plans by the Philippines to build on Zhongye Dao Island in the South China Sea were illegal.

"China has indisputable sovereignty over the Nansha Islands, including Zhongye Dao Island," said Chinese Foreign Ministry spokesperson Hong Lei at a regular press briefing in response to a question about the Philippines' intention to install a civil aviation satellite tracking system on the island.

The Civil Aviation Authority of the Philippines on Monday announced that it planned to build the tracking system and seven civil aviation radar stations. The tracking system will be used to monitor civil and commercial flights in the region, according to an official.

"Any action by the Philippines on Chinese territory is illegal," Hong said.

Philippine officials on Monday said that they had received two intimidating radio warnings from the Chinese Navy when they flew a civil plane to Zhongye Dao Island on Jan. 7.

According to the report, China also expelled other civil and military planes that flew over the region. Philippine officials claim they felt "threatened" about freedom of flights in the region.

"This sort of language is an alarmist talk, which intends to exaggerate regional tensions with ulterior motives," Hong said.

China firmly opposes the Philippines' illegal occupation of Chinese territory in the region, Hong said, noting that the Philippines had despatched troops and begun construction on eight reefs around the Nansha Islands including Zhongye Dao since the 1970s.