File photo dated July 2016 shows Chinese H-6K bomber patrolling islands and reefs including Huangyan Island in the South China Sea. (PHOTO / XINHUA)

The China Coast Guard announced late Tuesday night that it had expelled four Philippine citizens who had illegally entered China's Huangyan Island in the South China Sea on Sunday.

In a statement, coast guard spokesman Gan Yu said that four individuals from the Philippines illegally entered the island's reef on Sunday.

The China Coast Guard will, as always, conduct rights protection and law enforcement activities in the waters under Chinese jurisdiction

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The coast guard lawfully warned and expelled them, handling the situation professionally, he said.

Gan emphasized that China has indisputable sovereignty over Huangyan Island and its adjacent waters, and has always resolutely countered any infringement by the Philippines.

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"The China Coast Guard will, as always, conduct rights protection and law enforcement activities in the waters under Chinese jurisdiction, firmly safeguarding national sovereignty and maritime interests," he added.