China reaffirmed its indisputable sovereignty over Nansha Islands and its adjacent waters and protested the Philippines\' plan to explore oil and natural gas in this area. Chinese Foreign Ministry spokesman Hong Lei made the remarks at a regular press briefing when asked to comment on Philippine Secretary of Energy Jose Almendras\' remarks on inviting foreign investors to explore two oil and gas blocks claimed by China, China\'s News Agency (Xinhua) reported. \"It is unlawful for any country or company to explore oil and gas in sea areas under Chinese jurisdiction without the permission of the Chinese government,\" said Hong. He urged relevant countries to adhere to the spirit of the Declaration on the Conduct of Parties in the South China Sea and refrain from taking moves that will complicate or aggravate the dispute, and make due efforts for the peace and stability of the South China Sea.