Foreign Minister Julie Bishop has appealed for European Union backing in pushing back at China's land grab in the South China Sea, amid new reports that China is about to build on a disputed shoal.

Ms Bishop cited Australia's support for sanctions against Russia after its annexation of Crimea as a reason for the EU to support the Philippines against Chinese expansion.

The Philippines said on Wednesday it was "gravely concerned" that Chinese boats were preparing to build structures at the disputed Scarborough Shoal in the South China Sea, despite a ruling by an international tribunal in The Hague in July that China had no right to the waterway.

The Philippines released photos that it said showed Chinese ships, including a dredger, near the chain of reefs and rocks.