MOSCOW, July 21 (Xinhua) -- At least two people were killed and another two wounded by a group of unidentified gunmen before explosions rocked a hydro-electric station in Russia's North Caucasus region on Wednesday, news agencies reported.
The gunmen, believed to be militant fighters, entered the station at 04:20 a.m. Moscow time (0020 GMT) to place explosives and shot two guards dead, local police were quoted as saying.
One hour later, three explosions occurred with an interval of five to six minutes near the small town of Baksan in the North Caucasus republic of Kabardino-Balkaria, damaging part of the facilities and triggering a fire at the first and second floors of the power plant.
A fourth explosion was reported later, but causing minor impact.
Local authorities played down the risks of any floods as the water gate has been timely closed. Neither would the local electricity supplies be affected as electric power has been dispatched from other stations to the area.
Meanwhile they did not rule out the existence of other explosive devices at the power plant, which has already been cordoned off. Orders have been given to beef up security of all the power plants in southern Russia.
Local police has called the incident a terrorist attack. A law enforce source was cited by the RIA Novosti news agency as saying that the same group of assailants may be responsible for an earlier attack on police.
"At 3:15 a.m. (2315 GMT Tuesday) a police building was attacked with a grenade launcher in the city of Baksan. There were no casualties," said the source.
Baksan hydropower plant was built between 1930-1936.
On June 11, a total of six TV and radio broadcasting stations were attacked overnight at various districts of the republic, causing neither casualties nor disruption of normal operation of the stations.
Violence is common in Russia's mainly Muslim North Caucasus republics, especially Chechnya, Dagestan and Ingushetia, with militants frequently targeting police and officials as representing the Russian authorities.
Moscow claimed to tackle the problem of unemployment, clan rivalry and corruption as these are viewed as the reasons for violence in the region.