Two Vietnamese-flagged fishing vessels with 11 crew members on board were intercepted last Tuesday afternoon as they illegally trespassed through the North Natuna Sea, between the Natuna Islands and Cape Ca Mau on the southernmost tip of Vietnam, the Jakarta Post reported Sunday.

The Vietnamese fishermen were also found using a trawl to catch fish, which is forbidden in Indonesia, the newspaper said.

The vessels have violated the Law on fisheries in Indonesia and their crew could be subject to a maximum sentence of six years’ imprisonment and 20 billion rupiah ($1.4 million) fine.

As of January, Indonesia’s Maritime Affairs and Fisheries Ministry had detained 23 fishing vessels - 18 foreign and five domestic - for flouting the law. Of the foreign vessels, 11 were Vietnamese and the remaining seven were Malaysian.

Last year, Indonesia destroyed 86 Vietnamese fishing boats for illegally catching fish in its waters. Vietnam has several times called on Indonesia not to use violations against Vietnamese fishing boats and fishermen in a manner that goes against the strategic partnership between the two countries.

Vietnam’s Fisheries Resources Surveillance Department has also said it is working to raise awareness of maritime boundaries and international maritime laws among its fishermen, apart from conducting frequent patrols to prevent potential violations.