The Philippines on Sunday accused China of "incursion" after more than 200 militia boats were spotted near a disputed reef in the South China Sea, in a rare rebuke of its superpower neighbour.
The Philippine coast guard detected the boats "in line formation" at the boomerang-shaped Whitsun Reef around 320 kilometres (175 nautical miles) west of Palawan Island on March 7.
"We call on the Chinese to stop this incursion and immediately recall these boats violating our maritime rights and encroaching into our sovereign territory," Defence Secretary Delfin Lorenzana said in a statement.
"This is a clear provocative action of militarizing the area. These are territories well within Philippine Exclusive Economic Zone."
Lorenzana said the government was considering "appropriate action" to take to protect Filipino fishermen, the country's marine resources and maintain peace and stability in the area.
Foreign Secretary Teodoro Locsin said on Twitter he had lodged a diplomatic protest over the ships.
The Chinese embassy in Manila did not respond to a request for comment.
A government task force charged with monitoring the contested waters announced Saturday the detection of around 220 "Chinese Maritime Militia Vessels" earlier this month.
"Despite clear weather at the time, the Chinese vessels massed at the reef showed no actual fishing activities," the agency said.
The United States has previously accused China of using maritime militia to "intimidate, coerce and threaten other nations" over its claims to almost the entire South China Sea.
The resource-rich waterway is also contested by several countries, including the Philippines.
China has ignored a 2016 international tribunal decision that declared its assertion as without basis.
Philippine-China relations have improved under President Rodrigo Duterte, who has tried to steer his country away from the ambit of the United States -- its former colonial master -- to pursue greater economic cooperation with its giant neighbour and American rival.
But Duterte's shift has failed to stem Chinese ambitions in the sea or unlock much of the billions of dollars of promised trade and loans.
He has repeatedly said conflict with China would be futile and that the Philippines would lose and suffer heavily in the process.
Lorenzana, however, has been more outspoken.
In August he accused China of illegally occupying Filipino maritime territory, saying the nine-dash line used by Beijing to justify its alleged historic rights to the key waterway was a fabrication.
His remarks at the time came amid a fresh row over the disputed Scarborough shoal, which China seized from the Philippines in 2012 following a tense standoff.
In 2019, the Philippines also complained after hundreds of Chinese ships were seen near Pag-asa island, also known as Thitu, which the country branded as "illegal".