BEIJING/MANILA: China has condemned a mission by four Philippine ships to re-supply Philippine troops on a disputed South China Sea atoll, saying the vessels had entered its waters in the Spratly Islands without its permission.

The Philippines said on Wednesday it had successfully sent supplies to its troops stationed on a World War Two-era transport ship-turned-military outpost on the atoll despite attempts by China's coast guard to block it.

While China is in dispute with several of its neighbours over its extensive claims in the South China Sea, its relations with the Philippines have been particularly fraught recently over the issue, especially since Ferdinand Marcos Jr took over as Philippine president last year.

"Philippine supply ships and two coast guard ships entered the waters ... in China's Nansha Islands without permission from the Chinese government," China Coast Guard spokesperson Gan Yu said a post on its website, using China's name for the Spratly Islands.

The atoll in the area is known as Ayungin in the Philippines, while China calls it the Renai Reef. Also known as the Second Thomas Shoal, it is 105 miles (109 km) off the Philippine island of Palawan.

A small number of Philippine troops live on board the old navy transport ship, the BRP Sierra Madre, which the Philippines grounded on the shoal in 1999 to reinforce its sovereignty claim.

China Coast Guard said in its post that it issued stern warnings and added it firmly opposed the illegal Philippe transport of materials to the ship that "sits on the beach" illegally.

The Philippines last completed a resupply mission to the grounded ship on Sept. 8. A month earlier, a China Coast Guard vessel fired water cannon at a Philippine supply boat during a similar attempt, drawing condemnation from the Philippines and old ally the United States.

China has told the Philippines to tow the vessel away but Manila has rejected the demand. 

The Philippine National Security Council (NSC) said its re-supply and rotation mission was completed despite attempts by a significant number of China Coast Guard and Chinese Maritime Militia to "harass and interfere" with it.

"These missions are a legitimate exercise of the administrative functions of the Philippine government," the NSC said.

China claims sovereignty over almost the entire South China Sea, pointing to a line on its maps that cuts into the exclusive economic zones of Vietnam, the Philippines, Malaysia, Brunei and Indonesia. The Permanent Court of Arbitration in 2016 said that the line on China's maps had no legal basis.