The Philippines vowed Monday to take "all appropriate actions" for the removal of floating barriers allegedly installed by the Chinese coast guard at a disputed reef to stop Filipinos accessing the traditional fishing ground.

A 300-metre (328-yard) long floating barrier was found across the entrance of Scarborough Shoal in the South China Sea last week during a routine resupply mission to Filipino fishermen plying the waters near the Chinese-controlled reef.

China, which seized Scarborough Shoal from the Philippines in 2012, deploys coast guard and other vessels to patrol the fishing ground.

The floating barrier prevents fishing boats from entering the shoal's shallow waters where fish are more abundant.

Philippine officials previously accused the Chinese coast guard of installing the barrier shortly before the Bureau of Fisheries and Aquatic Resources ship arrived at the shoal last Wednesday.

Several media outlets, including AFP, were on board the BRP Datu Bankaw and saw the barrier.

"We will take all appropriate actions to cause the removal of the barriers and to protect the rights of our fishermen in the area," National Security Adviser Eduardo Ano said in a statement Monday.

Ano said the Philippines condemns the installation of barriers, arguing such action "violates the traditional fishing rights of our fishermen whose rights... have been affirmed by the 2016 Arbitral ruling."

Chinese foreign ministry spokesman Wang Wenbin hit back Monday, saying Scarborough Shoal was "an inherent part of China" and China had "indisputable sovereignty over it and its surrounding waters".

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.

Under the 1982 United Nations Convention on the Law of the Sea, which China helped negotiate, countries have jurisdiction over the natural resources within about 200 nautical miles (370 kilometres) of their shore.

China claims sovereignty over almost the entire South China Sea, while several other countries, including the Philippines, have overlapping claims to parts of it.

Beijing has ignored the 2016 international court ruling that its claims have no legal basis.

The Philippine foreign ministry said Monday it would "take all appropriate measures to protect our country's sovereignty and the livelihood of our fisherfolk", without elaborating.

Filipino fishermen say that China's actions at Scarborough Shoal are robbing them of a key source of income and a place to shelter safely during a storm.