Indonesian President Joko Widodo visited Natuna in Riau Islands in South China Sea on Thursday, sending a clear message about Indonesia's pledge to protect its sovereignty over areas it claims in the disputed waters.
The chief security minister and the foreign minister also accompanied the Indonesian president on his visit to the islands.
Indonesian officials described this move as the strongest message that has been given to China over the issue.
A presidential palace statement said Widodo will hold a limited Cabinet meeting in order to discuss the developments in Natuna Islands on board a warship sailing around Natuna waters on Thursday.
"In the course of our history, we've never been this stern (with China). This is also to demonstrate that the president is not taking the issue lightly," the Chief Security Minister, Luhut Pandjaitan told The Jakarta Post.
The Indonesian archipelago is made up of thousands of islands and among all those islands, Natuna islands and its surrounding waters are the closest to the Nine-Dash Line. Based on this demarcation, China claims that the waters constitute part of the country's "traditional fishing grounds" and their coast guard and fishing fleet often operate there.
However, Indonesia's Foreign Minister Retno Marsudi rejected China's claim on Wednesday and said the waters around Natuna islands are in Indonesian territory.
Both Indonesian and Chinese vessels have had a number of face-offs between them but both sides have denied the matter being a territorial or diplomatic dispute.
The president's visit was also intended to promote infrastructure development in Indonesia's border areas.
"We want to show that Indonesia is a big country and we have to show this physically," Widodo said in a statement.