China claimed Indonesia has infringed into its territorial waters, media reports said.

The exploratory drilling began in July near the Natuna islands within Indonesia's exclusive economic zone, which overlaps China's expansive "nine-dash line" territorial claim covering much of the sea, reports Nikkei Asia.

In addition to the protests, China has sent coast guard vessels into the area to increase pressure, Indonesian government sources told Nikkei Asia, citing eyewitness accounts.

China has territorial disputes across the South China Sea. The Philippines, Vietnam, Malaysia, Brunei and Taiwan have all made claims. Beijing has intensified activity near the Natuna islands since 2019, escalating tensions with Jakarta, the Japanese media reported.