Russia will open a new facility on Tuesday to continue destroying its formidable arsenal of chemical weapons, the world's biggest, as part of its drive to eliminate all such weapons by 2012.

Located near Leonidovka in the central Penza region, around 550 km (350 miles) southeast of Moscow, it is the sixth of seven such facilities Russia plans to build.

Russia and its Cold War-era foe the United States held more than 71,000 metric tonnes of deadly chemical agents in 1997, more than 90 percent of the world's chemical weapons stockpiles. Russia's arsenal alone stood at 40,000 tonnes.

Under the 1997 Chemical Weapons Convention, Moscow and Washington committed themselves to completely destroy all their stockpiles of chemical weapons by 2012.

The new Leonidovka facility holds 6,885 metric tonnes of VX, sarin and soman nerve agents, about 17 percent of Russia's declared chemical weapons stockpile.

"This is now the sixth chemical weapons destruction facility brought on line. Obviously, it will enhance Russia's destruction capacity to meet that (2012) deadline," Michael Luhan, chief spokesman for the Organisation for the Prohibition of Chemical Weapons, said by telephone from The Hague.

"At this point in time, the U.S. has now achieved 50 percent (chemical weapons) destruction."

Russia has destroyed 10,500 tonnes of toxic agents, or about a quarter of its chemical weapons stockpile, and plans to raise the figure to 18,000 tonnes by the end of 2009, Valery Kapashin, head of Russia's federal directorate for safe storage and destruction of chemical weapons, told local media this month.

"During the fourth stage, all (Russian) chemical weapons stockpiles will be eliminated in 2012," he said.

The OPCW's Luhan said Russia had begun work on its seventh and last chemical weapons destruction facility "about 10 days ago". The facility, at Pochep in the Bryansk region west of Moscow, will dispose of some 7,500 tonnes of sarin, soman and VX. VX is the most potent of all nerve agents.

Thousands of people, including many civilians, died an agonising death in the 1980s when Iraq's late dictator Saddam Hussein used shells filled with sarin in a war against Iran and against his country's rebellious Kurdish population.

In 1995, Japanese doomsday sect Aum Shinri Kyo sprayed sarin on Tokyo subway trains, killing 12 and making thousands ill.

"Just a milligram of deadly chemical agents is enough to kill persons living in an apartment," Sergei Baranovsky, president of Green Cross Russia, which monitors the elimination of Russia's chemical weapons, told Reuters.

"Now we still talk about tens of thousands of tonnes left."