UPDATE 1-Philippines, Vietnam press China over vessels massing in South China Sea

* Duterte 'really concerned' over boats swarm - spokesman
* Vietnam says vessels infringing on its sovereignty
* Philippines says China attache denies militia presence

(Recasts with Vietnam Foreign Ministry comments, coastguard
presence)
MANILA, March 25 (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.