Names waters in its exclusive economic zone as the North Natuna Sea, angering Beijing.

Indonesia has named waters in its exclusive economic zone that overlap with China’s expansive claim to the South China Sea as the North Natuna Sea, an assertion of sovereignty that has angered Beijing.

The decision announced last Friday by the Ministry of Maritime Affairs has been in the works since mid-2016 and was vital to law enforcement at sea and securing Indonesia’s exclusive economic zone, said Arif Havas Oegroseno, the deputy Minister for Maritime Sovereignty.

Beijing angry

A Chinese Foreign Ministry spokesman said the “so-called change of name makes no sense at all”.

“We hope the relevant countries can work with China for the shared goal and jointly uphold the current hard-won sound situation in the South China Sea,” he said.

China claims most of the South China Sea, putting it in dispute with many southeast Asian nations, and has carried out extensive land reclamation and construction on reefs and atolls to bolster its claims.

“The map of Indonesia has clear coordinates, dates and data, and the government would not negotiate with other nations that make unconventional claims... including those who insist on a map of nine broken lines,” Mr. Oegroseno said.

Philipppines also has claims to the South China Sea. But Filipino officials behind an arbitration case in which the Philippines won a resounding victory over China last year are expressing alarm that Beijing continues to defy the decision. Last week, they urged President Rodrigo Duterte to explore diplomatic and legal means by which to pressure China into complying.