Two communication satellites – one Russian, one American – have collided in space some 800 kilometres above Siberia.

It's the first crash of its kind, but NASA says it doesn't pose a threat to the International Space Station.

The accident occurred on Tuesday, creating a massive explosion with much debris scattering through space. It’s still unclear what caused the collision, which has become the first-ever involving two intact satellites.

The privately-owned American satellite – Iridium – was launched in 1997 and used for satellite telephone networks. The Russian Cosmos satellite was launched in 1993 and, according to NASA and Pentagon officials, had been non-operational for about 10 years.

According to NASA, debris creates some small risk to the ISS, which is located below the orbit where the accident took place. However, it will take several weeks before the full magnitude of the collision is determined.

There have been minor collisions in space before, but the scale of this crash is unprecedented. The satellites – one weighing about a tonne, the other almost 600 kilogrammes – crashed at a speed of 670 km per minute.

Officials said the incident will be investigated and analysed. Officals note that there are many hundreds of satellites in space and no ‘road rules’ regarding their orbits, therefore some people believe such accidents could have been expected.