Philippine President Rodrigo Duterte said Thursday he has ordered the military to occupy and fortify all Philippine-held islands in the disputed South China Sea to assert the country's claims amid what he says is a race to control territory in the area.

"We tried to be friends with everybody but we have to maintain our jurisdiction now, at least the areas under our control," he said during a visit to a military camp in western Palawan province.

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Duterte said he has ordered the armed forces to occupy and place Philippine flags on all islands, reefs and shoals controlled by the Philippines.

"There are about nine or 10 islands there, we have to fortify," he said. "I must build bunkers there or houses and provisions for habitation."

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It was unclear how Duterte's order can be executed. Some of the tiny reefs and outcrops would need expensive and logistically difficult reclamation work before structures could be built on them.

"The president wants facilities built such as barracks for the men, water (desalination) and sewage disposal systems, power generators (conventional and renewable), lighthouses, and shelters for fishermen," Defense Secretary Delfin Lorenzana said.

Duterte said he may visit one of the islands, Pag-asa, to raise the Philippine flag on Independence Day. He said money has been budgeted to repair the runway on Pag-asa, home to a small fishing community and Filipino troops.

Since taking office in June, Duterte has worked to mend ties with China that were strained under his predecessor over the territorial disputes.

An impeachment complaint has been filed against him that cites, among other things, his alleged failure to protest China's territorial expansion in the South China Sea.

Rival claimants, including the Philippines and Vietnam, have expressed alarm over Beijing's building of artificial islands in the disputed region.

"It looks like there's a race to grab islands," Duterte said. "What is ours now, we should get and make a strong point that it is ours."

He said he will rename Benham Rise -- a potentially resource-rich undersea region off the country's northeast coast -- the Philippine Ridge.

Benham Rise is on the opposite side of the Philippines from the area at dispute in the South China Sea. The U.N. Commission on the Limits of the Continental Shelf confirmed in 2012 that Benham Rise is part of the extended continental shelf of the Philippines.

Defense Secretary Delfin Lorenzana has said that Chinese survey ships were seen crisscrossing the Benham Rise area last year.