Indonesia marked its Independence Day on Wednesday by sinking 60 foreign ships seized for fishing illegally in the country's waters.

Maritime and Fisheries Minister Susi Pudjiastuti said the ships were sunk at eight locations across the Indonesian archipelago.

Pudjiastuti has organized the destruction of more than 200 illegal fishing boats since 2014. The government of President Joko "Jokowi" Widodo has taken a hardline stance against illegal fishing, partly driven by the need for Indonesia to show its neighbours, including China, that it is in control of its vast territory of 17,000 islands.

Many of the boats were captured off Indonesia's Natuna Islands, a point from which Indonesia's exclusive economic zone thrusts into the South China Sea. Beijing has described the area as a traditional Chinese fishing ground even though it is nearly 2,000 kilometers (1,250 miles) from the Chinese mainland.

The sinkings were carried out in a low-key fashion compared with previous occasions, when boats were blown to smithereens and their destruction broadcast live.

Pudjiastuti told a news conference in Ranai, a Natuna Islands port, that the ships were sunk off Ranai, Batam, Tarempa, Kalimantan, Maluku, and Sorong in West Papua to create artificial reefs.

"We do see at the moment the deterrent effect," she said. "I think it is already quite a strong message" to foreign countries and their fishing fleets.

Pudjiastuti said future ship sinkings would be done in a "less sensational way" but that would not mean Indonesia is relenting on its stance against illegal fishing.

The government originally planned to sink exactly 71 boats from the Philippines, Vietnam, Malaysia and China on Wednesday, which was the 71st anniversary of national independence.

Pudjiastuti said six other vessels would be sunk in Pangandaran on the southern coast of West Java, where the government plans to build a museum of illegal fishing with US and Norwegian help.

Local media reports said eight vessels were scuttled on Monday in the eastern Indonesian ports of Bitung and Ternate.

In March, Indonesia destroyed the Nigeria-flagged Viking with explosives. The ship was wanted around the world for illegally taking toothfish from southern waters.

Kotarumalos reported from Jakarta.