An ongoing increase in space debris poses a rising threat to economically vital orbital regions, say scientists gathering for a European forum on the issue.

Controlling space debris has become a focus for satellite operators worldwide, including those flying telecom, weather, navigation, broadcast and climate-monitoring missions, a release from the Paris headquarters of the European Space Agency said Thursday.

The level of space debris orbiting Earth is estimated at 29,000 objects larger than 4 inches and 670,000 pieces of around a half inch in size, experts said.

"Any of these objects can harm an operational spacecraft," Heiner Klinkrad, Head of ESA's Space Debris Office, said.

Collisions with fragments of just a few inches in size would be catastrophic, releasing hazardous debris clouds that could cause further catastrophic collisions, increasing debris in some orbits, he said.

"Space debris mitigation measures, if properly implemented by satellite designers and mission operators, can curtail the growth rate of the debris population," Klinkrad said. "Active debris removal, however, has been shown to be necessary to reverse the debris increase."

The 6th European Conference on Space Debris will be held at ESA's European Space Operations Center in Darmstadt, Germany, April 22-25.