Jakarta. The Indonesian government on Monday urged local fishermen to sail to North Natuna Sea to catch fish and help to assert the country's sovereignty in its northern maritime borders amid China's territorial claims.

Indonesia has lodged a "strong protest" with Beijing after last week's incident in which several Chinese fishing boats sailed into the waters off Riau Islands province accompanied by China's Coast Guard.

The Foreign Affairs Ministry said the area was within Indonesia's 200-nautical mile Exclusive Economic Zone (EEZ).

"The president has ordered us to beef up security in Natuna and assert our presence there. There are two things we can do: first, increase maritime patrols; second, send our fishermen there," Coordinating Minister for Political, Legal and Security Affairs Mahfud M.D. told reporters at his office in Central Jakarta on Monday.

He said the United Nations Convention for the Law of the Sea (UNCLOS) has granted Indonesia's sovereign rights over natural resources in the EEZ.

Mahfud said the government would encourage fishermen from Java's north coast to go fishing in the North Natuna Sea.

"We will mobilize fishermen from the northern coast of Java and also fishermen from other areas to catch fish there," Mahfud said after hosting a meeting with 120 fishermen from northern Java.

He said the government would provide assistance and security to fishermen operating in the North Natuna Sea.

"You will exercise your rights as citizens [to catch fish in Natuna]. You will do your bit to defend the country by going there and showing that the territory belongs to us," Mahfud said.