"It looks really terrible. I am shocked," said a space scientist, explaining that the reported test took place in a region thickly populated by satellites, including those used for monitoring storms and climate change.

"Space is not a playground for playing games," the scientist, outraged, said in an interview with AFP. "It's meant for the benefit of mankind."

The website space.com, quoting sources that it did not identify, said the January 11 strike against the old Chinese weather satellite had caused it to smash up into "hundreds of hundreds of pieces, fluttering through low Earth orbit."

"The mess of space junk does put other satellites, including the International Space Station, at some risk," space.com's Leonard David said, adding though that the chances of this were "very small."

The main repercussion of Chinese test has been fears of an arms race in space -- but debris is another big source of concern.

The space age reaches 50 years on October 4 this year -- the anniversary of the launch of the Soviet satellite Sputnik -- and there are hundreds of thousands of pieces whirling in orbit, the result mainly of exploded rocket stages and broken-up satellites.

David Wright, co-director of the Global Security Programme at the Union of Concerned Scientists (UCS), a US private advocacy group, said the satellite that was destroyed had a mass of 750 kilos (1,650 pounds) and had been orbiting at an altitude of 850 kilometers (520 miles).

Many commercial, military and navigational satellites orbit in the region of 900 kilometers (560 miles), he said. The maximum altitude of the International Space Station is around 450 kilometers (280 miles).

"The collision would be expected to completely fragment the satellite into millions of pieces of debris -- nearly 800 debris fragments of size 10 centimeters (four inches) or larger, nearly 40,000 debris fragments with size between one and 10 centimeters (half to four inches) and some two million fragments of size one millimeter (0.04 inch) or larger," said Wright.

"At the very high speeds these debris particles would have, particles as small as one millimeter (0.04 inch) can be very destructive."

Most satellites do not carry sufficient shielding for even tiny particles like this, and in any case shielding is ineffective against any debris larger than about one centimetre (half an inch) in size," said Wright in a statement.

The orbital region "is very heavily used by satellites for both civil and military uses, which are threatened by the added debris," he warned

Among those who voiced fears was Australia, which said on Friday that, in addition to worries about the militarisation of space, "we're concerned about the impact that debris from destroyed satellites could have on other satellites, which are very expensive pieces of equipment."

The danger from debris comes from the enormous speeds at which they travel, which means even very small pieces impact with high energy.

In 1996, a French spy satellite, Cerise, was wacked at about 50,000 kilometers (30,000 miles) per hour by a wheeling fragment left from an exploded Ariane rocket.

In June 1983, the windscreen of the US space shuttle Challenger had to be replaced after it was chipped by a fleck of paint measuring 0.3mm (0.01 of an inch), that impacted at four kms (2.5 miles) per second.

The worst debris clouds are in two main areas -- in low Earth orbit (LEO), which is at an altitude of between 800 and 1,500 kilometers (500 and 950 miles) above the Earth, and in geostationary orbit, about 35,000 kms (22,000 miles) away. In LEO, debris can take a decade or longer before eventually burning up on contact with Earth's atmosphere.

The Chinese test was first reported by US magazine Aviation Week and Space Technology and confirmed by the White House.

The only other anti-satellite test that has been carried out was in September 1985 by the United States. Its method, as China's, was a "kinetic energy" weapon, essentially slamming a projectile into the target.

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