The Philippines called for "restraint and sobriety" after an arbitration tribunal at The Hague gave it a sweeping victory in a case that it filed to challenge China's expansive claims in the South China Sea.
"We call on all those concerned to exercise restraint and sobriety," Foreign Minister Perfecto Yasay said after the ruling.
He also said the Philippines "strongly affirms its respect for this milestone decision as an important contribution to ongoing efforts in addressing disputes in the South China Sea".
The Philippines "reiterates its abiding commitment to efforts to pursue the peaceful resolution and management of disputes, with a view to promoting and enhancing peace and stability in the region", he added. A five-man tribunal convened by the Permanent Court of Arbitration struck down China's "historic rights", which Beijing used to justify a "nine-dash line" encircling over two-thirds of the 3.5 million sq km South China Sea.
China cited historical evidence and ancient maps in a "position paper" it released in 2014 to support the line.
But the tribunal ruled that the "nine-dash line" is inconsistent with an international treaty that uses land features, instead of historic rights, in determining sea borders.
Philippine President Rodrigo Duterte, who is hoping to engage China in talks on jointly tapping resources in the South China Sea, did not issue a statement.
However, he previously said Manila will not use any favourable ruling to "taunt" China.
Communications Minister Martin Andanar said the government's chief lawyer will submit to Mr Duterte a "synopsis" and an "interpretation" of the 479-page ruling within the next five days.
The Philippines' lead lawyer at the tribunal, Mr Paul Reichler, said the ruling "has very strong implications for the other coastal states in the South China Sea".
He added that the decision establishes that "it's just as illegal for China to apply (the nine-dash line) against Vietnam, Malaysia and Indonesia".
Philippine Supreme Court Justice Francis Jardeleza, who was solicitor-general when he led the country's team in the arbitration proceedings, said the ruling will be a "potent legal platform" to help achieve the "goal of effectively asserting our maritime entitlements".
Even before the tribunal released its decision, anti-China activists were holding a "victory party" to celebrate what they expected would be a ruling in favour of the Philippines.
There was dancing at a restaurant in Manila during a "thanksgiving lunch" hosted by groups that have been protesting against what they see as China's incursions into waters belonging to the Philippines.
Hundreds of activists released thousands of balloons in the red, blue, white and yellow colours of the Philippine flag, and chanted "Chexit" - a play on the phrase "China exit" - as they repeated calls for China to withdraw from Philippine-held territories.
Earlier in the morning yesterday, protesters marched towards the Chinese Embassy in Manila, carrying placards with slogans that read, "This is ours, China leave", and "Hands off Philippines".
Among the protesters were fishermen from communities that had suffered from China's blockade of the area around an atoll known as Scarborough Shoal.