MOSCOW: Space officials in Russia and the United States were yesterday tracking hundreds of pieces of debris that were spewed into space when a US satellite collided with a defunct Russian military satellite.

The crash, which Russian officials said took place Tuesday at about 1700 GMT above northern Siberia, is the first publicly known satellite collision and has raised concerns about the safety of the manned International Space Station (ISS).

The collision happened in an orbit heavily used by satellites and other spacecraft and the US Strategic Command, the arm of the Pentagon that handles space, said countries might have to maneuver their craft to avoid the debris.

“The collision of these two space apparatuses happened by chance and these two apparatuses have been destroyed,” Maj. Gen. Alexander Yakushin, first deputy commander of Russia’s Space Forces, told Reuters.

“The fragments pose no danger whatsoever to Russian space objects,” he said. When asked if the debris posed a danger to other nations’ spacecraft, he said: “As for foreign ones, it is not for me to say as it is not in my competency.”

The collision between the US Iridium 33 satellite and the Russian Cosmos-2251 military satellite occurred at about 780 km above the Russian Arctic.

That is an altitude used by satellites that monitor weather, relay communications and perform scientific observations. “It’s a very important orbit for a lot of satellites,” said Air Force Col. Les Kodlick from the US Strategic Command. “We believe it’s the first time that two satellites have collided in orbit.”

The US Joint Space Operations Center was tracking 500 to 600 new pieces of debris, some as small as 4 inches (10 cm) across, in addition to the 18,000 or so other man-made objects it previously cataloged in space, he said.

Russian Space Forces said it was monitoring debris that was spread over altitudes between 500 km and 1,300 km above Earth.

The priority is guarding the International Space Station, which orbits at 350 km, substantially below the collision altitude. One Russian and two US astronauts are currently aboard the station.

The orbit of the ISS can be changed by controllers from Earth but even a tiny piece of debris can cause significant damage to the space station as it travels at 8 km per second.

“If there is any threat to the ISS then there will be an announcement,” one Russian space official said. Another said there was little immediate threat to the station.

There are about 18,000 identifiable, man-made objects in space, including operational and defunct satellites, spent rocket boosters and debris. Experts said that while the risk of satellite collisions like Tuesday’s was exceptionally small, now one had occurred it made another more likely.

“The problem with collisions like this is that they don’t destroy satellites, they just create smaller ones, like fast moving shotguns, that are potentially much more damaging,” said Francisco Diego, a senior research fellow in physics and astronomy at University College London.