Philippines - US and Filipino troops fired missiles and artillery at an imaginary "invasion" force days after their governments objected to China's apparently "dangerous" actions in regional waters.

Thousands of US and Filipino troops on Monday conducted land, sea, and air maneuvers off the north coast of the Philippines.

The exercises are set against the backdrop of increasing tensions and confrontations between Chinese and Filipino vessels in the South China Sea.

US troops massed at a strip of sand dunes on Luzon Island's northwest coast let loose more than 50 live 155mm howitzer rounds at floating targets, presumably meant to simulate Chinese "invading" forces, about three miles off the coast.

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Filipino troops followed up by firing their own rocket barrage, simulating the wearing down of attackers, before the two forces launched an all-out assault with machine guns, Javelin missiles, and more artillery rounds.

Lieutenant General Michael Cederholm, commander of the US First Marine Expeditionary Force, told reporters that the exercise was meant "to prepare for the worst" by "securing key maritime terrain" in a way that was "designed to repel an invasion."

"Because of the regional problems that we have," said Major General Marvin Licudine, exercise director for the Philippines, "we have to already practice and orient ourselves in our own land in these parts."

Ongoing operations are designed to push back against China, whose officials have repeatedly claimed sovereignty over the South China Sea and Taiwan. Chinese forces have deployed hundreds of coast guard, navy, and other vessels to patrol the waters.

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In response to an incident last week that saw Chinese coast guard ships come into confrontation, via water cannons, with Filipino coast guard ships, Chinese foreign ministry spokesperson Lin Jian said the "China Coast Guard took necessary measures to expel them in accordance with the law."

"China urges the Philippines to stop making infringement and provocations at once and not to challenge China’s resolve to defend our sovereignty."