A civilian flight-tracking system the Philippines plans to install in the South China Sea is illegal, the Foreign Ministry said on Tuesday.

It also said Manila is igniting tension by accusing China of sending radio messages to Philippine commercial aircraft flying toward a Chinese island.

"The allegations from the Philippines are intentionally flaring up regional tensions with unconcealed purpose," Foreign Ministry spokesperson Hong Lei said.

"China has indisputable sovereignty over the Nansha Islands, including Zhongye Island. Any activities carried out by the Philippines on occupied Chinese territory are illegal," Hong said.

Philippine officials said on Monday they had received two radio warnings identified as originating from the Chinese navy when they flew a plane close to a Chinese island in the South China Sea on Jan 6.

The plane was actually flying toward another Chinese island, Zhongye Island. The Philippines illegally occupied some Chinese islands in the South China Sea, including Zhongye Island, in the 1970s.

The Philippines also said on Monday that it would install a civilian flight-tracking system on Zhongye Island.

The automatic dependent surveillance-broadcast machine, which identifies aircraft positions using satellite signals, will be operational by November, said Rodante Joya, acting director of the Civil Aviation Authority of the Philippines.

Joya said the system was part of a broader $209 million effort to more than double the country's commercial flight radar coverage.

Hong on Tuesday also rebuffed remarks by Japanese Prime Minister Shinzo Abe in an interview with the Financial Times about Japan's "concern" over China's construction on some of its islands in the South China Sea, and its attempt to explore oil and gas in the East China Sea.

The spokesperson said such activities are all within areas of Chinese sovereignty.