Washington  - A US satellite was destroyed in an unprecedented collision with a spent Russian satellite, raising fears of danger to other satellites and the international space station ISS, the space. com internet portal reported Thursday.

The collision between a commercial US communications satellite and Russia's Cosmos 2251 satellite, which had been turned off for years, occurred Tuesday at 0455 GMT above Siberia at a height of 790 kilometres, space. com said, quoting a statement by US space agency NASA.

"This is the first time we've ever had two intact spacecraft accidentally run into each other," said Nicholas Johnson, chief scientist of NASA's Orbital Debris Program Office at the Johnson Space Center in Houston. "It was a bad day for both of them."

According to officials a huge debris field of more than 500 pieces formed, which could pose a threat to other satellites. It would take at least two days before the scope of the debris field could be assessed, NASA spokesman Michael Carey told the CBS news channel.

However, experts believed the danger to the ISS, which flies in an orbit well below the impact height, is limited. (dpa)