MANILA (Reuters) - Philippine President Rodrigo Duterte expressed concern to China's ambassador about Chinese vessels massing in the South China Sea, his spokesman said, as Vietnam urged Beijing to respect its maritime sovereignty.
International concern has grown in recent days over what the Philippines has described as a "swarming and threatening presence" of more than 200 Chinese vessels that it believes were manned by maritime militia.
The boats were moored at the Whitsun Reef within Manila's 200-mile exclusive economic zone.
"The president said we are really concerned. Any country will be concerned with that number of ships," Duterte's spokesman, Harry Roque, told a regular news conference.
Brunei, Malaysia, the Philippines, Taiwan, China and Vietnam have competing territorial claims in the South China Sea, through which at least $3.4 trillion of annual trade passes.
Roque said Duterte reaffirmed to China's ambassador, Huang Xilian, that the Philippines had won a landmark arbitration case in 2016, which made clear its sovereign entitlements amid rival claims by China.
China's maritime assertiveness has put Duterte in an awkward spot throughout his presidency due to his controversial embrace of Beijing and reluctance to speak out against it.
He has instead accused close ally the United States of creating conflict in the South China Sea.
China's embassy in Manila did not respond to a request for comment on Duterte's meeting.
On Wednesday it said the vessels at Whitsun Reef were fishing boats taking refuge from rough seas. A Philippine military spokesman said China's defence attache had denied there were militia aboard.
Vietnam's Foreign Ministry spokeswoman Le Thi Thu Hang on Thursday said the Chinese vessels at the reef, which Hanoi calls Da Ba Dau, had infringed on its sovereignty.
"Vietnam requests that China stop this violation and respect Vietnam's sovereignty," Hang told a regular briefing.
A Vietnamese coastguard vessel could be seen moored near the disputed area on Thursday, according to ship tracking data published by the Marine Traffic website.
Hang said Vietnam's coastguard was "exercising its duties as regulated by laws", including international law.