A spacewalk for work on the International Space Station ended abruptly yesterday when a water-like liquid started building up inside an Italian astronaut's helmet, NASA officials said.

US astronaut Chris Cassidy and Italy's Luca Parmitano were less than an hour into a planned six-hour outing when Parmitano reported what seemed to be water inside his helmet.

"My head is really wet and I have a feeling it's increasing," Parmitano radioed to flight controllers in Houston.

Thinking it might be his drink bag leaking, Parmitano drained the bag, but in the weightless environment of space, blobs of liquid continued to collect in his helmet..

NASA called off the spacewalk and Cassidy hastily cleaned up equipment while Parmitano waited in the station's airlock.

Inside the station, NASA astronaut Karen Nyberg and cosmonauts Pavel Vinogradov and Fyodor Yurchikhin took off Parmitano's helmet and sopped up the excess water with towels.

The cause of the leak remained unclear,