The world's largest radio telescope began operating in southwestern China Sunday, a project Beijing says will help humanity search for alien life.

The Five-hundred-metre Aperture Spherical Radio Telescope (FAST), nestled between hills in the mountainous region of Guizhou, began working around noon, the official Xinhua news agency reported.

Built at a cost of 1.2 billion yuan ($180 million), the telescope dwarfs the Arecibo Observatory in Puerto Rico as the world's largest single-dish radio telescope, with twice the sensitivity and a reflector as large as 30 football fields, it said.

FAST will use its vast dish, made up of 4,450 panels, to search for signs of intelligent life, and to observe distant pulsars -- tiny, rapidly spinning neutron stars believed to be the products of supernova explosions.

China sees its ambitious military-run, multi-billion-dollar space programme as symbolising the country's progress. It plans a permanent orbiting space station by 2020 and eventually a manned mission to the moon.

Chinese President Xi Jinping celebrated the launch, with reports Sunday that he had sent a congratulatory letter to the scientists and engineers who contributed to its creation.

The telescope represents a leap forward for China's astronomical capabilities and will be one of several "world-class" telescope projects launched in the next decade, said Yan Jun, head of China's National Astronomical Observation (NAO), according to Xinhua.

In a test run before the launch, FAST detected electromagnetic waves emitted by a pulsar more than 1,300 light-years away, state media reported an NAO researcher as saying.

Earlier Xinhua cited Wu Xiangping, director-general of the Chinese Astronomical Society, as saying that the telescope's high degree of sensitivity "will help us to search for intelligent life outside of the galaxy".

Experts have been hunting for alien intelligence for six decades, pointing radio telescopes at stars in the hope of discovering signals from other civilisations, but have not yet found any evidence.

- 'Wildest imagination' -

Last month a "strong signal" detected by a Russian telescope searching for extraterrestrial signals stirred interest among scientists, but experts said it was far too early to make conclusions about its origin.

But the new FAST telescope could "lead to discoveries beyond our wildest imagination," Douglas Vakoch, president of METI, a group seeking to send messages to space in search of alien life, told Xinhua.

Construction of FAST began in 2011, and local officials relocated nearly 10,000 people living within five kilometres (three miles) to create a quieter environment for monitoring. Cell phones in the area must be powered off to maintain radio silence.

In the past China has relocated hundreds of thousands of people to make way for large infrastructure projects such as dams and canals.

The area surrounding the telescope is remote and relatively poor. State media said it was chosen because there are no major towns nearby.

The villagers will be compensated with cash or housing. The budget for relocation is 1.8 billion yuan ($270 million), it was reported, more than the cost of constructing the telescope.

China has poured money into big-ticket science and technology projects as it seeks to become a high-tech leader, but despite some gains the country's scientific output still lags behind.

At the beginning of this month, reports said 600 apartments had been built so far with the funds.