Amid increasing tensions in the South China Sea, India said its navy would protect the country's interests, which include oil exploration blocs off the coast of Vietnam, in the disputed waters.

Indian navy Chief Adm. D.K. Joshi on Monday said that although India isn't a direct claimant in the South China Sea, its main concern was "freedom of navigation in international waters," The Hindu newspaper reports.

Chinese regulations, approved last week by the coastal province of Hainan, which administers the South China Sea for China, appear to authorize Chinese police to board foreign vessels around disputed islands in the area, The Wall Street Journal reports.

Joshi said the "modernization" of the Chinese navy was "a major, major cause for concern" and that India would work out its options and strategies.

The admiral cited India's state-run Oil and Natural Gas Corp.'s exploration blocks in the South China Sea as a reason for the navy to show its presence when necessary.

"Not that we expect to be in those waters very, very frequently but when the requirement is there, for example, in situations where our country's interests are involved, for example ONGC, ONGC Videsh, etc., we will be required to go there and we are prepared for that," Joshi said.

Joshi added: "Now, are we preparing for it? Are we having exercises of that nature? The short answer is yes."

ONGC Videsh has invested $600 million in oil and gas exploration in three offshore deep-water blocks on the southern Vietnamese coast.

China maintains it has sovereignty over all the South China Sea, while Vietnam asserts competing claims over parts of the sea, including the Spratly Islands. The disputed waters are also claimed in whole or in part by the Philippines, Taiwan, Brunei and Malaysia.

The South China Sea's oil reserves are estimated to be 23 billion-30 billion tons, with natural gas reserves believed to total about 16 trillion cubic meters, says China Ministry of Land and Resources.

Chinese Foreign Ministry spokesman Hong Lei, when asked what the Chinese government would do if the Indian navy went to protect its oil interests in the South China Sea, said that China has indisputable sovereignty over the islands in the sea and adjacent waters, Voice of America reports.

Hong added that Beijing opposes oil and gas development in the South China Sea and that he hopes concerned countries will respect China's position and rights.

State-run China National Offshore Oil Corp. in August opened 26 offshore blocks -- 22 of which are in the South China Sea -- for development in cooperation with foreign companies.