The Philippines accused China's coast guard Friday of illegally seizing fishing equipment near a disputed shoal in the South China Sea, sparking a fresh spat with Beijing.
Scarborough Shoal, one of several reefs controlled by China, is one of the region's richest fishing grounds and a flash point between the two countries.
The Philippine foreign ministry said it has lodged a diplomatic protest over the "illegal confiscation" by the Chinese coast guard in May of floating devices, known as payao, that are used to catch fish.
It also "resolutely objected" to China issuing radio challenges to Philippine aircraft conducting maritime patrols in areas of the sea claimed by Manila.
China's foreign ministry defended the coast guard, saying they had carried out law enforcement activities and "their actions are understandable".
It also accused Philippine military aircraft of invading Chinese airspace in another disputed section of the sea and urged Manila to "immediately stop illegal provocative activities".
Scarborough shoal is 240 kilometres (150 miles) west of the Philippines' main island of Luzon.
China seized it in 2012 after a tense standoff with then Philippine president Benigno Aquino, who sent a warship to the area. Aquino later backed down.
Beijing claims almost the entire South China Sea despite competing partial claims from Brunei, Malaysia, the Philippines, Taiwan and Vietnam.
It has ignored a 2016 international tribunal ruling that declared its assertion as without basis.
Philippine-China relations have improved under President Rodrigo Duterte who has cosied up to Beijing in search of trade and investment.
But security issues in the sea helped convince the government to delay quitting a key US military pact earlier this year.