JAKARTA • Indonesia's President yesterday ordered an expansion of offshore oil exploration and commercial fishing in the waters near the Natuna Islands, the latest in a new campaign to assert sovereignty over the area in the South China Sea.

Indonesia has taken unprecedented steps in the past week to lay claim to the island chain, whose gas-rich waters Beijing says are subject to "overlapping claims".

President Joko Widodo travelled to Natuna for the first time last week to hold a Cabinet meeting aboard a warship, in what Indonesian officials described as the strongest message given to China.

"Out of 16 blocks around Natuna, only five are producing," Mr Joko said before a Cabinet meeting to discuss development of the area. "We want to push so that they enter (the) production stage sooner."

The government also wants to develop Indonesia's commercial fishing industry in Natuna, whose waters are regularly trawled by vessels from Vietnam, the Philippines, China and other nearby nations. Mr Joko said fishing production around Natuna was only around 9 per cent of its potential now.

Indonesia's navy has stepped up patrols around the islands after a series of face-offs between Indonesian naval vessels and Chinese fishing boats. Parliament on Tuesday approved a near 10 per cent hike in defence spending to fund, among other things, major upgrades to military facilities in Natuna.

Jakarta objects to Beijing's inclusion of waters around the Natuna Islands within China's "nine-dash line", a demarcation line used by Beijing to show its claims.

"We do not recognise China's nine-dash line and its claims of a traditional fishing zone," said Chief Security Minister Luhut Pandjaitan. "Natuna is our territory. We want stability in the area."

REUTERS