JAKARTA (AFP) - Indonesia sank dozens of impounded foreign boats to mark Independence Day, an official said on Wednesday (Aug 17), as President Joko Widodo steps up a campaign to stop foreign fishermen from "stealing" in its waters.

Since elected, President Joko Widodo has intensified a campaign to exercise Indonesia's maritime sovereignty and has sunk and blown up scores of foreign vessels.

"Today we offer 60 boats" to be scuttled in eight locations, fisheries ministry official, Mas Achmad Santosa, said.

"This is a gift (for Indonesia) and goes to show our consistency in enforcing the law," Santosa added.

But unlike past boat-sinking events, which were broadcasted on national television, Wednesday's ceremony was markedly toned down, with officials barring media coverage.

Officials have also refused to disclose the vessels' countries of origin.

Previously, Indonesia has scuppered boats from countries including China, Vietnam and Philippines, with Beijing particularly angered by the gesture.

Tension between Jakarta and Beijing has escalated in recent months as Chinese fishing boats have clashed with Indonesian government vessels, prompting Widodo to visit the Natunas islands on a warship in June.

On Tuesday, he pledged to defend "every inch" of Indonesia's land and maritime territory in a state-of-the-nation address.

Unlike several of its Southeast Asian neighbours, Indonesia has long maintained it has no maritime disputes with China in the South China Sea and does not contest ownership of any territory there.

But Beijing's claims overlap Indonesia's exclusive economic zone - waters where a state has the right to exploit resources - around the Natunas.