China has started assembling the world's largest radio telescope, which will have a dish the size of 30 soccer fields when completed, Xinhua News Agency reported.

The 500-meter Aperture Spherical Radio Telescope, known as FAST, sits in a bowl-shaped valley between hills in the southwestern province of Guizhou, images posted online show.

Technicians began attaching 4,450 triangular panels to the telescope's reflector on Thursday, Xinhua said.

FAST will be the world's largest single-aperture telescope, it said, overtaking the Arecibo Observatory in the US territory of Puerto Rico, which is 305 meters in diameter.

For years Chinese scientists have relied on data collected by others in their research, and the new telescope is expected to greatly enhance the country's capacity to observe outer space, Xinhua said.

"Having a more sensitive telescope, we can receive weaker and more distant radio messages," Wu Xiangping, director-general of the Chinese Astronomical Society, was quoted by Xinhua as saying.

"It will help us to search for intelligent life outside of the galaxy and explore the origins of the universe."

The dish will have a perimeter of about 1.6 kilometers, Xinhua said, and there are no towns within 5 km, giving it ideal surroundings to listen for signals from space.

The region's karst topography, a landscape of porous rock fissured with deep crevices and underground caves and streams, is ideal for draining rainwater and protecting the reflector, it added.

Construction of the telescope started in March 2011 and is scheduled to finish next year, Xinhua said.

The 500-meter Aperture Spherical Radio Telescope is under construction in Southwest China's Guizhou province. Jin Liwang / Xinhua