Nasa and Russia’s space agency cancelled a spacewalk by two Russian cosmonauts just as they were preparing to exit the International Space Station late on Wednesday because of an apparent coolant leak from an attached space capsule.

Nasa’s Johnson Space Centre said Sergey Prokopyev and Dmitri Petelin were not in danger, nor were other astronauts on the space station.

The cosmonauts had donned spacesuits and depressurised an airlock when the leak appeared on a live video feed.

It was the second time the Russian cosmonauts had to cancel the spacewalk. As in the first attempt on November 25, the pair had planned to move a radiator from one module attached to the space station to another.

In that first attempt, a problem arose with coolant pumps on the cosmonauts ’Russian-built Orlan spacesuits.

In Wednesday’s incident, ground specialists saw a stream of fluid and particles on a live video feed from space,along with a pressure drop on instruments, emanating from the Soyuz MS-22 capsule that had carried Prokopyev and Petelin, along with Nasa astronaut Frank Rubio, to theInternational Space Station in September.