JAKARTA, Indonesia — When Indonesia recently — and quite publicly — renamed the northernmost waters of its exclusive economic zone in the South China Sea despite China’s claims to the area, Beijing quickly dismissed the move as “meaningless.”

It is proving to be anything but.

Indonesia’s increasingly aggressive posture in the region — including a military buildup in its nearby Natuna Islands and the planned deployment of naval warships — comes as other nations are being more accommodating to China’s broad territorial claims in the South China Sea.

The two countries had three maritime skirmishes in 2016 involving warning shots, including one in which Indonesian warships seized a Chinese fishing boat and its crew.

Indonesia is challenging China, one of its biggest investors and trading partners, as it seeks to assert control over a waterway that has abundant resources, particularly oil and natural gas reserves and fish stocks.