Nasa has aborted a spacewalk at the International Space Station (ISS) because of a dangerous water leak in an astronaut's helmet.

The leak was so bad that Luca Parmitano, Italy's first spacewalker, could not hear or speak as the spacewalk came to an abrupt end.

He asked his spacewalking partner, Christopher Cassidy, for help getting back inside the ISS.

The source of the leak wasn't immediately known but one possible source being considered was the helmet drink bag that astronauts sip from during spacewalks.

Footage from Nasa shows the incident unfold.