China said on Monday agreements like the one reached last week by the United States and the Philippines allowing for a US military presence at five Philippine bases raised questions about militarization in the South China Sea.
The United States is keen to boost the military capabilities of East Asian countries and its own regional presence in the face of China's assertive pursuit of territorial claims in the South China Sea, one of the world's busiest trade routes.
The United States and its regional allies have expressed concern that China is militarizing the South China Sea with moves to build airfields and other military facilities on the islands it occupies.
Asked about the base deal, Chinese Foreign Ministry spokeswoman Hua Chunying said that US-Philippine cooperation should not be targeted at any third party nor harm other nations' sovereignty or security interests.
"I also want to point out that recently the US military likes to talk about the so-called militarization of the South China Sea," Hua told a daily news conference.
"Can they then explain, isn't this kind of continued strengthening of military deployments in the South China Sea and areas surrounding it considered militarization?"
China claims most of the energy-rich waters through which about US$5 trillion in ship-borne trade passes every year. Neighbors Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims.
The United States says it takes no sides in the disputes but wants to ensure free navigation through the sea. It has said it will increase what it calls freedom-of-navigation operations by its navy ships through the waters.
US allies Malaysia and Australia both reiterated on Monday calls for freedom of navigation through the South China Sea.
"We've been extremely consistent in saying that our activities will continue, that we will send our ships and our planes to that part of the world as we require, as it is necessary in accordance to international law," Australian Defense Minister Marise Payne said after meeting her counterpart in Malaysia.
Malaysian Defense Minister Hishammuddin Hussein said that free movement in the air and waters should continue.
China has never interfered with freedom of navigation and has stressed that some of the equipment it is installing on small islands and reefs will facilitate navigation.