A Chinese defense spokesman said on Monday that China firmly opposes any construction activities by the Philippines on Chinese islands and reefs that it has illegally occupied in the South China Sea.

Jiang Bin, the spokesman for China's Ministry of National Defense, made these remarks at an online news briefing in response to media reports citing satellite images that showed the Philippines is accelerating infrastructure upgrades on illegally occupied islands and reefs in the Nansha Islands.

The reports indicated that Manila plans to expand a harbor on Mahuan Island and extend the runway on Zhongye Island.

Jiang stated that China has indisputable sovereignty over the Nansha Islands and their adjacent waters. "We firmly oppose construction activities by the Philippine side on all illegally occupied Chinese islands and reefs, including Zhongye Island and Mahuan Island," he said.

Jiang warned that China will take necessary measures to safeguard its territorial sovereignty and maritime rights and interests.