NEW DELHI A little over a fortnight before China conducted sea trials for its first aircraft carrier, an Indian naval ship slipped into the South China Sea.
INS Airavat, an amphibious assault vessel designed to launch troops on enemy beaches, was on a show-the-flag mission in July when it was challenged as it sailed from Vietnam's Nha Trang port near the deep-water harbour of Cam Ranh Bay.
A caller identifying himself as an official of the Chinese navy warned the ship on an open radio channel that it was entering Chinese waters as it steamed towards the Vietnamese port of Haiphong, the Indian foreign ministry said.
Nothing happened, the ship sailed on, and both India and China have since played down the incident, with New Delhi saying the vessel was well within international waters in the South China Sea and that there was no confrontation.
China's foreign ministry also dismissed the report, saying there was no truth to it.
But the news has stoked concern that the navies of the two rapidly growing Asian giants could be on a collision course as they seek to protect trade routes and lock in the supply of coal, minerals and other raw material from faraway lands.
The Airavat is part of a fleet based in the Andaman islands, nearer to Indonesia than the Indian mainland, where New Delhi is spending $2 billion (1.24 billion pounds) to set up a military command.
The islands are also the gateway to the Bay of Bengal, which is shared by India, resource-rich Myanmar, Bangladesh and western Thailand.
"It was a bit slow in the beginning, but the command is being strengthened now. It will become a premier base by 2015," said a defence ministry official in New Delhi on the Andamans plan, launched under a "Look East" policy started in 2001.
"The movement of commercial shipping in the area is just as important to us as it is to others, including China," said the official, who spoke on condition of anonymity.
"If you have to, you can get to the South China Sea fairly quickly, you are sitting right there."
India's trade with East and Southeast Asia dwarfs that with Europe or the United States, and the country imports most of its much-needed edible oil, coal and minerals from Southeast Asia.
Beijing, concerned about the flow of its energy supplies, is seeking a chain of friendly ports in the Indian Ocean, stretching from Gwadar on the Pakistani coast to Chittagong in Bangladesh.
The Indian navy, worried about what it sees as Chinese encirclement at sea, is deepening defence ties with long-term partner Vietnam, and cautiously stepping up its presence in the South China Sea, whose mineral and gas resources are claimed by six countries, including China.
"While the Chinese do not consider the Indian Ocean to be India's ocean or even India's strategic backyard, they do consider the South and East China seas to be China's seas," said former Indian navy commander Probal Ghosh, now a senior fellow at Observer Research Foundation, a New Delhi think tank.
India and China have on the surface a friendly relationship, but the two nations fought a brief border war in 1962. China is close to Pakistan, India's arch-enemy, while it has suspiciously eyed New Delhi's warm ties with Vietnam.
S.D. Muni, a former Indian ambassador to Laos and now a visiting professor at the National University of Singapore, said he expected more flare-ups as the two expanding navies begin to rub against each other.
"They are getting bigger in size, extending their reach, probing each other's defences," he said.
Viewed from Beijing, India's military has expanded its area of operations westward to the Persian Gulf and eastward to the Malacca Straits, encompassing the key sea lanes that three quarters of Chinese oil imports must transit.
"The Indian navy entering the South China Sea is a relatively new development," said Zhao Gancheng, director of South Asia studies at the Shanghai Institute for International Studies. "I think it shows that the Indian navy is currently expanding its scope of activities."
He said the navies of India and Vietnam had established a certain degree of cooperation, and carried out joint exercises. China and India, on the other hand, appeared to have little interaction with each other, increasing the risk of misunderstanding.
Traditionally, India's navy has long been the biggest player in the Indian Ocean - after the United States - and it was the only Asian state to operate an aircraft carrier as far back as 1961.
That carrier has been retired but it has another one in service and two more on order, including one to be based in the eastern sector.
Media reports say the Indian navy is shifting focus from the western command, which faces Pakistan, to the eastern command and the Andamans. Its nuclear submarines will be based in the east, along with guided missile destroyers, stealth frigates and maritime patrol aircraft.
China, by contrast, is just starting out on a carrier task force, and analysts say it could be up to 10 years before it assembles a battleship group.
"The Indian navy is certainly the most ambitious and strategically significant of all the service arms," said Shashank Joshi, an associate fellow at London's Royal United Services Institute.
"Its doctrine places remarkable emphasis on non-violent diplomatic roles - what it calls showing power and projecting presence. That is the thin end of India's wedge into East Asia."