Jakarta: Indonesian President Joko Widodo has held a cabinet meeting on a warship in the Natuna Islands in a defiant gesture to China that it has sovereign rights over the disputed waters in the far north of the archipelago.

Diplomatic tensions have been rising after three clashes between Chinese fishing vessels and the Indonesian navy in the region in as many months.

Indonesia is not a claimant in the territorial dispute in the South China Sea and China acknowledges that the Natuna Islands belong to Indonesia.

However part of the waters surrounding the islands, which are rich in marine life, fall within both Indonesia's exclusive economic zone and the so-called "nine-dash line" on which China bases its claim over most of the South China Sea.

China has strongly protested Indonesia's pursuit of its fishing vessels and demands Jakarta release apprehended crew members, saying they were operating in Chinese "traditional fishing grounds".

In the latest incident, China claimed a fisherman was injured when the Indonesian Navy apprehended one of 12 Chinese fishing vessels it said were operating illegally in the area over the weekend.

Mr Joko's press office released a statement on Thursday saying the development of the Natuna Islands was the government's main priority.

"In this working visit President Joko Widodo will lead a meeting on developing the economic potential of the Natuna Islands as one of Indonesia's foremost verandahs and national strategic areas," it said.

Mr Joko, who is only the third president to visit Natuna, was accompanied on Thursday by a number of high-powered ministers including Foreign Minister Retno Marsudi, Chief Security Minister Luhut Panjaitan and Maritime Affairs and Fisheries Minister Susi Pudjiastuti, who is famous for her tough stance on poaching, including the sinking of foreign trawlers.

Indonesia, which is keen to encourage foreign investment from China, has played down previous maritime spats with its powerful neighbour.

"I think it is a big deal," Evan Laksmana, from the Centre for Strategic and International Studies in Jakarta, said of Mr Joko's visit.

"Just because we are committed to maintaining a good relationship with China does not mean Indonesia is willing to sell out its waters. That is the delicate balance Jokowi is trying to tread - it needs to be made clear that the islands and waters surrounding the islands are ours."

Since the mid-1990s, Indonesia has played an "honest broker" role as a non-claimant in the South China Sea.

However Mr Laksmana said China needs to be prepared for Indonesia to be much more assertive if its sovereign rights continue to be tested.

An international tribunal convening in The Hague will soon hand down its decision in a landmark legal case that the Philippines has brought against China, including the legality of its nine-dash line claim.

"Both domestic and international pressure has been mounting for Indonesia to take a position with regard to the upcoming Permanent Court of Arbitration ruling," Mr Laksmana said.

Melda Kamil Ariadno, a professor of international law at the University of Indonesia, said she believed China was deliberately provoking Indonesia.

"Very soon the Permanent Court of Arbitration will issue a verdict and I believe it will cancel China's claim of a nine-dash line. That's why China is doing some manoeuvres."

Asked if the conflict would lead to deteriorating economic relations between the two countries, Dr Melda said: "Remember, it is not just us who needs China, but China needs us. So we do need to have a good relationship but it should not come at the price of sovereign rights and sovereignty."

with Karuni Rompies

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