A Japanese deep-space probe became the first ever to collect asteroid dust during a seven-year voyage that ended with its return to Earth over the Australian desert this year, Japan said Tuesday.

The news crowns with success the journey of the unmanned Hayabusa probe, which five years ago made a pinpoint landing on an asteroid 300 million kilometres (186 million miles) from Earth -- about twice as far as the sun.

Since the probe's return in June, scientists had carried out a lengthy analysis of the samples it brought back to confirm they were genuinely extraterrestrial after technical problems during the mission.

"It's a world first and a remarkable accomplishment that it brought home material from a celestial body other than the moon," Japan's science and technology minister, Yoshiaki Takagi, told a news conference in Tokyo.

Hayabusa, which means falcon, blasted off in 2003 for its lonely odyssey, which at times appeared doomed. At one stage the probe lost contact with Earth for seven weeks, a glitch that added three years to its space voyage.

It made a pinpoint landing in 2005 on the potato-shaped, revolving asteroid Itokawa, but an attempt to fire a pellet to whirl up dust failed, casting doubt on whether the probe had collected any extraterrestrial material.

Japan cheered when Hayabusa ended its voyage in June, when it burnt up on reentry over the Australian outback -- but not before releasing its heat-proof and sealed pod, which was picked up from the desert sand.

The Japan Aerospace Exploration Agency (JAXA) confirmed that the pod did indeed contain minute particles, but it did not know for sure whether these were the valued bits of asteroid they were seeking, or simply contaminants.

On Tuesday, after analysis using electron microscopes, JAXA said it had confirmed that about 1,500 particles are indeed material from a rock and that "almost all of them are extra-terrestrial and come from Itokawa".

Scientists believe asteroids can help reveal secrets about the birth of the solar system 4.6 billion years ago.

The celestial bodies are believed to retain materials from the solar system's earliest days, unlike scorched remains such as meteorites or materials on Earth which have been transformed through high pressure and heat.