The International Space Station (ISS) has sprung a leak after being hit by space junk or a micrometeorite.

Mission flight controllers in Houston and Moscow noticed a drop in pressure on Wednesday night and, after a search on Thursday, astronauts discovered a 2mm hole in the Russian section of the station.

At that size it would have taken just 18 days for the crew to run out of air if they had not spotted the leak.

The damage was found by closing hatches to each module one at a time, and European Space Agency (ESA) astronaut Alexander Gerst initially plugged the gap with his finger, before using duct tape to cover the hole, preventing more air leaking into space.

During a live feed from the ISS, Nasa's ground control were heard to comment: "Right now Alex has got his finger on that hole and I don't think that's the best remedy for it."