Civilians on board Philippine fishing boats sailed Wednesday towards a China-controlled reef off the Southeast Asian country to distribute provisions to Filipino fishermen and assert their rights to the disputed waterway.

The trip to the waters around Scarborough Shoal comes two weeks after China Coast Guard vessels fired water cannon at two Philippine government boats in the same area, in the latest maritime incident between the countries.

Waving tiny Philippine flags and chanting "the Philippines is ours, China out!", about 200 people boarded five commercial fishing vessels that sailed out of a northern port in the morning, escorted by a number of tiny outriggers.

A few hours later, a lone Philippine Coast Guard boat met the convoy in open seas and stood guard as it handed out food and fuel to Filipino fishermen and dropped a dozen orange buoys marked "WPS is Ours".

WPS is the acronym for the West Philippine Sea, Manila's name for the South China Sea waters immediately west of the Philippines.

Later, the group issued a statement saying it would "proceed to the second phase of its voyage, aiming to reach the vicinity of Panatag Shoal for another round of supply distribution to Filipino fisherfolk in the area".

The Philippine Coast Guard in Manila said it was deploying more vessels to escort the convoy.

A spokesman for the convoy told reporters via a messaging app that there was "no Chinese presence" where the vessels had distributed assistance to fishermen.

He declined to disclose the exact location of this phase of the voyage, except to say the boats were "still far from the shoal".

The group had said it received reports of a "heavy presence" of Chinese vessels near the Scarborough Shoal.

Called Panatag in the Philippines, the Scarborough Shoal has been a potential flashpoint since Beijing seized it from Manila in 2012.

The fish-rich reef is about 240 kilometres (150 miles) west of the Philippines' main island of Luzon and nearly 900 kilometres from Hainan, the nearest major Chinese land mass.

- 'The world is watching'

China claims almost the entire South China Sea, brushing off rival claims by the Philippines and other countries, and ignoring an international ruling that its assertion has no legal basis.

To press its claims, Beijing deploys coast guard and other boats to patrol the waterway and has turned several reefs into artificial islands that it has militarised.

"This civilian supply mission is not just about delivering supplies, it's about reaffirming our presence and rights in our own waters," convoy organiser Edicio Dela Torre said in a statement Wednesday.

"The world is watching, and the narrative of rightful ownership and peaceful assertion is clearly on our side," Dela Torre added.

Tensions over the disputed waters and reefs have intensified in the past 18 months as Manila has pushed back against China's growing assertiveness.

This is the second civilian convoy organised by the Atin Ito group, whose name is Tagalog for "This is Ours".

A previous trip to the South China Sea in December was aborted due to shadowing by Chinese vessels.