The government of the Philippines says it has logged what it calls "illegal incursions" into its waters by 287 boats with Chinese militia aboard.
The country's task force on the South China sea said in a statement that the incident may prompt possible diplomatic actions.
It's the latest sign of cracks in the relationship between China and the Philippines after a period of warming.
Philippines' foreign ministry has repeatedly complained to China in recent weeks about Chinese vessels in its waters
The country has also boosted its presence in the South China Sea by sending more patrols in the area, even though President Rodrigo Duterte is pro-China.
China claims almost the entire South China Sea, but the borders have long been disputed by several countries in the region.
Chinese officials have previously denied there are militia aboard its fishing boats.