The Philippines on Saturday accused Chinese coast guard ships of "dangerous" manoeuvres after they repeatedly blocked a vessel delivering supplies to Filipino fishermen at a reef off the Southeast Asian nation's coast.
The incidents happened near the China-controlled Scarborough Shoal on Thursday and Friday, several days after the Philippine Coast Guard made similar accusations against Chinese boats in the same area.
Scarborough Shoal -- a triangular chain of reefs and rocks in the disputed South China Sea -- has been a flashpoint between the countries since China seized it from the Philippines in 2012.
Since then, Beijing has deployed patrol boats that Manila says harass Philippine vessels and prevent Filipino fishermen from reaching a lagoon where fish are more plentiful.
In the latest incidents, a Chinese navy ship, China Coast Guard vessels and other Chinese boats shadowed a Philippine Bureau of Fisheries and Aquatic Resources (BFAR) vessel that was bringing food and fuel to Filipino fishermen, allowing them to spend more time at sea and pursue a larger catch.
AFP correspondents and journalists from several local outlets were on board the Philippines' BRP Datu Tamblot for the three-day round trip.
The Datu Tamblot and the China Coast Guard vessels issued repeated radio challenges to each other, each side accusing the other of encroachment on their waters.
On four occasions, Chinese coast guard vessels briefly blocked the Datu Tamblot by crossing its bow and stopping in its path as it neared the shoal.
"It's not permitted for any vessel to cross the bow of another vessel because it is very dangerous," Philippine Coast Guard Commodore Jay Tarriela told a news conference in Manila on Saturday.
Tarriela, who is the coast guard's spokesman for the West Philippine Sea, said such actions could "cause a collision".
Despite the Chinese actions, the Datu Tamblot was able to get within a few kilometres of the shoal and deliver 21,000 litres (5,550 gallons) of diesel and other provisions to 19 Philippine fishing boats, Tarriela said.
Fishermen in small wooden outriggers bobbed around in the water as they waited to receive blue plastic jerry cans of diesel and food parcels from the Datu Tamblot crew.
"Every time we come here, I'm really nervous," said Joe Saligan, 44, a third-generation fisherman who has been plying the waters around Scarborough Shoal for 20 years.
"Maybe they will do what they did before, they might fire a water cannon or force us to leave," he said.
"Next time they might bring a gun. I hope that will not happen because we are not trained to fight, we're just here for our livelihoods," Saligan added.
Salvador Achina, 49, said the food and fuel deliveries were a "big help", enabling the fishermen to go further out to sea.
BFAR spokesman Nazario Briguera said more than 385,000 Filipino fishermen depended on the waters to the west of the country for their livelihoods.
Scarborough Shoal is 240 kilometres (150 miles) west of the Philippines' main island of Luzon and nearly 900 kilometres from the nearest major Chinese land mass of Hainan.
China claims almost the entire sea and has ignored an international tribunal ruling that its assertions have no legal basis.
Tense standoffs between China and the Philippines around disputed reefs in the South China Sea last year saw collisions between vessels from the two countries and Chinese ships blasting water cannon at Philippine boats.
