Prime Minister Manmohan Singh Sunday cautioned Indian oil majors against complacency in acquiring hydrocarbon assets overseas, which he said was vital for the fuel-starved country to achieve energy security.

In what was a clear reference to the manner in which ONGC Videsh lost a deal to China in acquiring an oil asset in Angola, the prime minister told a global oil conference here that Indian firms must exercise greater professionalism.

"We can no longer be complacent and must learn to think strategically, to think ahead and to act swiftly and decisively," Manmohan Singh told the inaugural session of Petrotech 2005 conference.

"I find China ahead of us in planning for the future in the field of energy security."

In the past, Chinese national oil companies have outbid state-run ONGC Videsh Ltd of India in some major deals to acquire oil exploration blocks in Angola and Sudan with their speed and aggressive nature of bidding.

Some of the exploration blocks India lost produce more oil than Bombay High - 400,000 barrels a day.

In one of the blocks offered in Sudan, ONGC lost a deal to China National Petroleum Corp since the Indian cabinet took 10 days to discuss the matter, officials at the conference said.