MANILA, Philippines: Under a defense agreement with the U.S., four new military bases will be located in various parts of the Philippines, including in a province facing the South China Sea, announced President Ferdinand Marcos Jr.

Last month, Marcos granted the U.S. access to four sites, on top of five existing locations under the 2014 Enhanced Defense Cooperation Agreement (EDCA), amid China's growing assertiveness in the South China Sea and towards Taiwan.

"There are four extra sites scattered around the Philippines - there are some in the north, there are some around Palawan, there are some further south," Marcos told reporters on the sidelines of the Philippine army's founding anniversary.

The Philippines and the U.S. are to announce the locations of the bases soon, Marcos said, adding that the bases will boost the country's ability to defend the "eastern side" of its largest island, Luzon. Luzon is the closest main Philippine island to self-ruled Taiwan, which China claims as its own.

China's foreign ministry has reiterated its stance that the U.S. was increasing tensions by strengthening its military deployments in the region, adding that countries should be "vigilant" and avoid being used by the U.S.

"We generally believe that defense cooperation between countries should be conducive to regional peace and stability, and should not be aimed at third parties or harm the interests of third parties," spokesperson Wang Wenbin told reporters at a regular news briefing.

Speaking before Philippine troops, Marcos said they should remain vigilant, as the external threat to security was becoming more difficult.

"The external security environment is becoming more complex. It is becoming more unpredictable," Marcos said.