Philippine Defence Secretary Gilberto Teodoro said that the region is the "spearhead of the Philippines as far as the northern baseline is concerned".

He said the garrison would be strengthened as the Philippine Navy described it "pivotal" shift in the nation's defense posture.

The Luzon Strait is a choke point for access between the South China Sea and the Philippine Sea, and China's navy uses it to move carrier strike groups and destroyers out to the open Pacific. Access to the strait is necessary for Chinese interests in the event of a Taiwan Strait conflict.

The PLA Navy could use it to threaten Taiwan's eastern shores or to maintain a cordon around the island. Conversely, the strait would be a key access point to the Taiwan Strait and South China Sea for American and allied forces.

Mr Gilberto's announcement of plans to reinforce Batanes is the latest development in an extended back-and-forth between Manila and Beijing.

China claims a large swath of the Philippine EEZ as its own, despite an arbitral court ruling in the Philippines' favour in 2016.

Chinese forces regularly harass Philippine service members and fishermen in the Spratly Islands, and the People's Liberation Army has turned a string of reefs in the region into strategic airbases, complete with air defenses and military-grade runways.

China is also leaning into greater confrontation. This week, a senior researcher at a Chinese think tank said that it was time for China to "show our swords" and defend its unrecognised maritime claims.

Wu Shicun, chairman of the Huayang Centre for Maritime Cooperation and Ocean Governance, wrote that "long-term peace and stability in the South China Sea cannot be achieved only by China's unilateral restraint".

"We will take timely action against any stirring up of trouble . . . and dare to show our swords when necessary," Mr Wu said in the piece, published in Beijing's Global Times.