Dozens of Russian shoppers injured in gas attacks

More than 70 people became ill after gas was released in a store in St Petersburg and devices containing bottles were found in three other outlets of the store chain. Police said they believed a commercial dispute or blackmail was behind the incidents.

A spokesman for the Emergency Situations Ministry, Viktor Beltsov, said 78 people sought medical care and 66 of them were kept in hospital. But a spokesman for St Petersburg police, Vyacheslav Stepchenko, was only able to confirm 15 hospital admissions.

Mr Stepchenko said preliminary tests found the gas to be methyl mercaptan, the effects of which are little known. The US Health and Human Services' Agency for Toxic Substances and Disease Registry says methyl mercaptan is a gas smelling like rotten cabbage that is both naturally occurring and manufactured for use in plastics and pesticides.

Mr Stepchenko said one staff member of the home-supplies chain had found a suspicious box containing ampoules attached to wires and a timer. The woman inadvertently broke one of the ampoules but apparently was not harmed, he said.

Those who sought medical care were from another branch of the chain.

A store spokesman told police they had received letters threatening to disrupt the company's sales during the holiday gift-buying period. Police are considering the incidents as "hooliganism".