India's navy chief says the modernization of China's navy is a source of major concern and has pledged to protect India's interests in the South China Sea.

India's state-run Oil and Natural Gas Corporation (ONGC) has a stake in a gas field off the coast of Vietnam. China claims almost all of the South China Sea. The Philippines, Brunei, Malaysia, Taiwan and Vietnam also have claims to parts of the region, including the Spratly Islands, which are believed to sit atop mineral deposits.

Indian Navy Chief Admiral D.K. Joshi told reporters in New Delhi on Monday that ONGC is engaged in three energy exploration blocks in the area, and that “whenever the requirement is there to defend our country's interest in the maritime domain, the navy has the mandate to do it.” He said India's navy is preparing for any situation and conducting relevant exercises.

Joshi noted the modernization of China's navy is “truly impressive” and a “major concern for us, which we continuously evaluate and work out our options and our strategy.”

The admiral also asserted that disputes over freedom of navigation in the South China Sea should be resolved by the concerned parties in line with international treaties, such as the United Nations Convention on the Law of the Sea.

Despite expanding trade ties, mutual mistrust between India and China lingers, especially as the two growing powers emerge as competitors for more influence and resources in Asia.

China has reacted strongly to India's efforts to search for oil in the South China Sea. For its part, India is uneasy with a growing Chinese presence in the Indian Ocean as Beijing builds ports and infrastructure in neighboring countries such as Sri Lanka and Bangladesh.