WASHINGTON (Reuters) - A privately owned U.S. communications satellite collided with a defunct Russian satellite in the first such collision in space, a U.S. military spokesman said on Wednesday.

The collision, which took place on Tuesday in low-earth orbit, involved a spacecraft of privately owned Iridium Satellite LLC and a “non-operational” Russian communications satellite, said Air Force Lieutenant Colonel Les Kodlick of the U.S. Strategic Command.

“We believe it’s the first time that two satellites have collided in orbit,” he said.

The command’s Joint Space Operations Center was tracking 500 to 600 new bits of debris, some as small as 10 centimeters (3.9 inches) across, in addition to the 18,000 or so other man-made objects it has catalogued in space, Kodlick said.

The collision occurred at roughly 780 kilometers (485 miles), an altitude used by satellites that monitor weather and carry telephone communications among other things, he said.

“It’s a very important orbit for a lot of satellites,” he said.

The International Space Station flies at a lower altitude and is the command’s No. 1 priority in attempting to prevent collisions, Kodlick said.