India's navy chief said Monday that Beijing's growing maritime strength was a "major, major cause for concern" and pledged to help a state energy firm in its contentious search for oil in the South China Sea.

Admiral D.K. Joshi told journalists that China's push to upgrade its navy was "truly impressive" and said that India had to adapt its own strategy accordingly.

"It is actually a major, major cause of concern for us, which we continuously evaluate and work out our options and our strategies for," Joshi said.

China, which put its first aircraft carrier into service in September, has been locked in a series of disputes over strategic islands in the region, including with Vietnam and the Philippines over territory in the South China Sea.

India, which also currently has one carrier in service, signed a pact with Vietnam in October last year to expand oil exploration in the South China Sea.

India is scheduled to receive a second aircraft carrier from Russia by 2013 and it plans to build a third itself.

Although Beijing has urged New Delhi not to push ahead with the project for the sake of "peace and stability", Joshi said that the Indian navy was ready to support state energy firm ONGC and had carried out exercises in preparation.

"In certain sectors ONGC Videsh has certain interests. It has energy exploration blocks, three in number, and since it is an area of Indian interest the Indian Navy, should there be a need, would stand by," Joshi said referring to the firm's international subsidiary.

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

"Are we holding exercises for that nature? The short answer is 'yes'".

The admiral also argued that disputes over freedom of navigation within the South China Sea must be resolved in line with international treaties.

"Not only us, but everyone is of the view that they have to be resolved by the parties concerned, aligned with the international regime, which is outlined in UNCLOS (United Nations Convention on the Law of the Sea), that is our first requirement," he said.

Analysts said India's interest was focused on China's long-term ambitions rather than its immediate acquisitions such as the Soviet-era aircraft carrier.

"The accretion of China's military capability will always be a matter of concern to India and the Chinese navy is one such example," New Delhi-based analyst Uday Bhaskar said.

"The Chinese have a very well-planned ship-building programme and they are going to be a navy to be reckoned with," Bhaskar said, adding that Beijing planned to launch scores of new warships and scores of submarines by 2020.

New Delhi is also wary of growing Chinese influence around the Indian Ocean, where Beijing has funded or plans to invest in major infrastructure projects, including ports in Sri Lanka, Bangladesh and military-ruled Myanmar.

China's military budget officially reached $106 billion in 2012, an 11.2 percent increase.

According to a report issued by the Pentagon in May, Beijing is pouring money into advanced air defences, submarines, anti-satellite weapons and anti-ship missiles that could all be used to deny an adversary access to strategic areas, such as the South China Sea.

At a key Communist Party congress earlier this month, outgoing President Hu Jintao urged China to push forward fast-paced military modernisation and set the goal of becoming a "maritime power".

India's first aircraft carrier was bought 55 years ago from Britain and was scrapped in 1997. The second aircraft carrier was also sold by Britain to India in 1987 and it is still in service.

India and China fought a brief border war in 1962 and still have unresolved territorial disputes.