Philippine President Rodrigo Duterte ordered the country's military to build structures in the islands in South China Sea. The president said Thursday that he plans to visit the disputed region and raise the Philippine flag.

"We have to maintain our jurisdiction over South China Sea," Duterte told reporters in Palawan, according to the ABS-CBN network. "I have ordered the Armed Forces to occupy all" the islands claimed by the Philippines and raise the country's flag on them.

Duterte will be visiting the island of Thitu   on the country's Independence Day in June. The Thitu island is located close to the Subi Reef, which is one of the seven manmade islands in the Spratlys that China is accused of militarizing with surface-to-air missiles.

Read: Are China And Japan At War Over The South China Sea?

China claims most of the South China Sea, through which over $5 trillion of maritime trade passes annually. Brunei, Malaysia, the Philippines and Taiwan also have conflicting claims to the waters. According to the U.S. Energy Information Administration, it is estimated that 11 billion barrels of oil and 190 trillion cubic feet of natural gas sit below the surface of the South China Sea.

China has been accused of accelerating its military developments with military aircraft and ships near the disputed islands. Beijing's island building and military prowess have been slammed by several Southeast Asian countries and the West. China has also built runways and ports on some islands in the region, claiming it adds to the safety of the region.

Last month, tensions between China and the Philippines escalated after the latter accused Beijing of sending survey ships into its 200-nautical mile exclusive economic zone.

Chinese ships were found in recent months near its coast and a warship was spotted 70 miles off its western coast in the South China Sea, Philippine Defense Secretary Delfin Lorenzana said last month. However, China dismissed the claims saying the Chinese vessels had the right to freedom of navigation in the waters.