The European Space Agency (ESA) has called for increased international cooperation to head off a threat posed to its network of satellites by debris flying around space .

"No country can stand or act alone," Jan Woerner, the chief of ESA, told an international conference in the western German city of Darmstadt on Tuesday.

"It's clear to us that the issue of space debris is serious," he said at the opening of the four-day summit, which has been held every four years since 1993.

About 400 engineers, scientists and managers are to join representatives of universities, as well as all major space travel nations at the conference, which is being held at ESA's Satellite Control Centre.

Experts gather in Germany to debate the threat of space debris https://t.co/BSXCjHSO5l pic.twitter.com/p1fY2f29xE — Al Jazeera English (@AJEnglish) April 19, 2017

In addition to large pieces of debris that have been flung off satellites or remnants of rockets, ESA officials believe that there are about 750,000 objects between one and 10cm in diameter flying around in space.

Many of the objects are travelling at an enormous pace, up to 56,000 kilometres per hour, which means that they can have the potential explosive force of a hand grenade on impact.

"We are very much concerned," said Rolf Densing, director of operations at ESA, also pleading for a worldwide effort to tackle the mess.



"This problem can only be solved globally."