By Subir Bhaumik
BBC News, Calcutta
The navies of the US, Australia, India, Japan and Singapore have begun a massive naval exercise, codenamed "Malabar", in the Bay of Bengal.
US Navy carrier USS Nimitz is part of the exercise
Thirty-four ships and submarines from the five countries have joined the six-day exercise, about 100 nautical miles off the Andaman archipelago.
Some analysts say the war games are an attempt by these countries to contain China's growing power.
The participants deny this, but Beijing has expressed its concerns.
"This will perhaps be the biggest ever peace-time joint naval exercise in Asia," Indian navy spokesman Captain Vinay Garg said.
The ships and submarines would take part in anti-piracy manoeuvres, reconnaissance and rescue missions and improve ways of working together, he said.
Left parties in India are protesting against the exercise
Two super-carriers of the US navy - USS Nimitz and USS Kitty Hawk of the Pacific fleet - will be joined by India's lone aircraft carrier, the INS Viraat, in the exercise.
A US nuclear submarine, USS Chicago, is also taking part.
India has denied claims that the exercise is aimed at China. "This is simply directed at ensuring security of the sea lanes of communication," Deputy Defence Minister Pallam Raju said.
The six-day exercise has been fiercely opposed by India's left-wing parties, who see it as "India's growing subservience" to the US.
The left, whose support is essential for the survival of India's Congress-led government, has organised demonstrations to oppose the exercise.
Chanting anti-US slogans, about 80 protestors boarded buses in Calcutta for Vishakhapatnam, a southern port city near the venue of the exercise.
Another group of left workers is scheduled to leave on Wednesday for Madras (Chennai), the capital of Tamil Nadu state, from where they will go to Vishakhapatnam where a protest rally is scheduled for Saturday.
In the past, India has held exercises with navies from Britain, France, Russia, Singapore and Vietnam.
A tri-nation event involving Brazil, India and South Africa is also due to be held in May 2008.