MANILA — The Philippines sent its top military officials on Friday to an island it occupies in the disputed South China Sea to reinforce the country’s claim.

Even before the military C-130 transport aircraft reached Pag-asa Island, also known as Thitu, the Chinese challenged the flight at least four times on radio as it passed through the region. China claims the island, as do Vietnam and Taiwan.

Defense Secretary Delfin Lorenzana, who led the trip, sought to play down the challenge from the Chinese, saying it was their “protocol” to question aircraft flying over what they regarded as their airspace. “No untoward incident happened,” he added.