The six-member crew of the International Space Station were forced  to evacuate to their Soyuz rescue vehicles today after spotting incoming debris that threatened to flatten their fragile craft.

"The space junk was detected too late for a ducking maneuver," the Interfax news agency quoted an unidentified source in the Russian space industry as saying.

"The six ISS crew members received instructions to transfer to the Soyuz vehicles," the Russian source said.

An official at Russian space control outside Moscow said by telephone that such incidents had occurred on past occasions and did not represent an emergency.

"If this is true, they would be following the normal procedure for evacuating the station if necessary," the mission control spokeswoman said.

"This is not an emergency operation. They have standing instructions to that effect," the spokeswoman said.

Three crew members were forced to briefly evacuate the ISS in an incident reported by international media in March 2009.

It was not immediately clear when the debris was expected to approach the station or what precisely was detected.

The crew is currently manned by three Russians and two Americans as well as a Japanese astronaut.