The centre of Moscow is enveloped in a mysterious cloud of noxious gas.
The foul smelling vapour spread across the city during the day, forcing residents to stay indoors.
The source of the stench, which polluted the Russian capital's commercial centre and some residential areas, is still unclear.
Government officials advised people to stay indoors as a precaution and not to panic. They blamed the smell on a leak at a local oil refinery, but the owner of the facility has denied any problem at the plant.
The smell is said to resemble rotten eggs, or hydrogen sulphide, which can be highly toxic.
