JAKARTA - A Vietnamese coast guard vessel on Sunday (May 21) reportedly intercepted an Indonesian maritime security patrol that was escorting five fishing boats caught poaching earlier.

Indonesia's Ministry of Marine Affairs and Fisheries said on Tuesday (May 23) that the Vietnamese fishing boats were stopped in Indonesian waters near the Natuna Islands, in the South China Sea. Vietnam, however, claims its fishermen were in its own waters during the incident.

But the clash on Sunday not only led to the Indonesian authorities losing custody of all five Vietnam-flagged fishing boats, it had detained earlier, but it also resulted in one of its own officers being held by the Vietnamese coast guard.

This comes just days after President Joko Widodo was in the Natunas to witness a major militrary exercise that involved more than 5,000 armed forces personnel on May 19.

It was also reminiscent of a similar confrontation in March last year, when a Chinese coast guard vessel intervened in the same way and freed the Chinese fishing boat, KM Kway Fey, after it was held by an Indonesian patrol. Jakarta later summoned the Chinese envoy to explain its coast guard's actions.

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Indonesia and Vietnam, however, will resolve the matter amicably through diplomatic channels, said Maritime Affairs and Fisheries Ministry secretary-general Rifky Effendi Hardjianto at a press conference in Jakarta on Tuesday .

The Indonesian official added that he had met with Vietnamese Ambassador to Indonesia Hoang Anh Tuan earlier on Tuesday to address the matter and agreed that they "will not fight at sea".

The five fishing boats were stopped by the Indonesian patrol on Sunday between 10am and 11.20am local time, after they were spotted poaching in Indonesia's Exclusive Economic Zone (EEZ) just off the Natunas in Riau Islands province, said Mr Rifky.

An EEZ is a zone extending 200 nautical miles from shore over which a state has special rights regarding the exploration and use of marine resources under the United Nations Convention on the Law of the Sea.

As the poachers were being escorted to land for processing by officers from the Maritime and Fisheries Resources Monitoring Directorate-General, a Vietnamese coast guard vessels showed up to obstruct their path at sea. It would later be joined by three more Vietnamese coast guard vessels, he added.

According to the Indonesian patrol craft's log, seen by The Straits Times, one of the Vietnamese coast guard vessels suddenly rammed against one of the fishing boats at about 1.10pm and it sank.