"This morning, Russia can tell the world that it has fulfilled the first stage in the disarmament of chemical weapons," Zinovy Pak told journalists.

Russia had promised to destroy by April 29 400 tonnes of chemical weapons -- or four percent of its 40,000-tonne stock, which includes sarin and VX nerve gas and is the largest in the world.

On Thursday morning, inspectors overseeing work at Russia's Gorny plant -- the only factory working full-time on destroying chemical weapons -- said that the plant had succeeded in destroying 400 tonnes as promised, Pak said.

Dismantling Russia's stocks of military plutonium and chemical weapons, which is seen as vulnerable to theft and sale in the corruption-tainted post-Soviet era, has become a main focus of international efforts to halt proliferation.

Russia has pledged to destroy its chemical weapons stock by 2012.

SPACE.WIRE