The Philippines said war games with the United States that ended Friday had showcased its resolve to fend off external aggressors, amid an escalating territorial dispute with China.

Philippine Defence Secretary Voltaire Gazmin also said the 12 days of exercises, involving more than 6,000 soldiers, had firmed up a 1951 mutual defence treaty between the longtime allies.

"This training activity... demonstrates our unequivocal resolve to support each other against the threats of external aggression and the enemies of freedom and liberty," Gazmin said in a statement.

The exercises were held amid the backdrop of a dispute between the Philippines and China over a shoal in the South China Sea, with both nations stationing vessels there for nearly three weeks to assert their sovereignty.

The Philippines and the United States had repeatedly emphasised the war games were not connected to the Scarborough Shoal issue, as they were an annual exercise planned well before the latest flare-up in tensions.

Nevertheless, the Philippines also sought to use the wargames to highlight its military alliance with the United States, amid warnings and threats from China over the South China Sea dispute.

One of China's ruling Communist Party newspapers ran an editorial calling for a small scale war with the Philippines to end the standoff, and its military on Thursday vowed to defend the country's territory.

"China's armed forces bear the responsibility for the task of defending the nation's territorial sovereignty," China's official Xinhua news agency quoted defence ministry spokesman Geng Yansheng as saying.

China claims all of the South China Sea as a historic part of its territory, even waters close to the coasts of the Philippines and other Southeast Asian countries, and hundreds of kilometres (miles) from its own landmass.

The Philippines says Scarborough Shoal is its territory because it falls well within its 200-nautical-mile exclusive economic zone, as recognised by international law.

The Philippines has called for arbitration through the United Nations to end the dispute, but China has refused.