MANILA, May 16 (Reuters) - A Philippine group leading a civilian supply mission in the South China Sea delivered food and fuel to Filipino fishermen despite being shadowed by Chinese vessels, its officials said on Thursday, calling it a "major victory".

Atin Ito (This is Ours) said a 10-member team sailed to the Scarborough Shoal a day before the civilian flotilla, composed of five commercial vessels and 100 small fishing boats, began its voyage on May .

"The mission achieved a major victory when its advance team reached the vicinity of Panatag Shoal on May 15 (and) was able to supply the fishers in the area," said Emman Hizon, Atin Ito spokesperson, using the local name of Scarborough.

Located inside Manila's 200 nautical-mile (370km) exclusive economic zone, the Scarborough Shoal is coveted for its bountiful fish stocks and a turquoise lagoon that provides safe haven for vessels during storms.

China said on Wednesday it has sovereignty over the shoal, which it calls Huangyan Island, and its adjacent waters. Chinese state broadcaster CCTV said the Chinese Coast Guard conducted "routine rights protection and law enforcement activities" in waters around the shoal on Wednesday.

Hizon told Reuters the advance team was part of the group's contingency plan in case China blocked the main flotilla, which he said would make its way back to port on Thursday after having sailing to a point about 50 nautical miles from the shoal.

Hizon said the larger flotilla was not needed because the fishermen, already supplied by the advance ships, left the area after being driven away by Chinese vessels.

A Philippine Coast Guard (PCG) aircraft deployed to monitor the situation at Scarborough Shoal on Wednesday spotted 19 Chinese vessels, including one Chinese navy ship, in the area where. The PCG said it was also monitoring two floating barriers at the southeastern entrance of the shoal.

The PCG was not part of the mission, but deployed vessels to provide safety and security for the civilian volunteers. The PCG said two Chinese Coast Guard ships shadowed Atin Ito boats.

China claims almost all the South China Sea, including parts claimed by the Philippines, Brunei, Malaysia, Taiwan and Vietnam, despite a 2016 ruling by the Permanent Court of Arbitration found that its sweeping claims have no legal basis.

(Reporting by Karen Lema and Adrian Portugal. Editing by Gerry Doyle)