Two killed in attack on Russian power station

* Blast hits North Caucasus hydroelectric power station

* Supplies to consumers not cut

MOSCOW, July 21 (Reuters) - Two security guards were killed in a suspected "terrorist act" when an explosion struck a hydroelectric power station in the Kabardino-Balkaria region of Russia's North Caucasus on Wednesday, officials said.

Russia is trying to contain an upsurge of attacks by rebels in the mainly Muslim provinces on its southern flank who took their war to the Russian heartland in March with suicide bombings on the Moscow metro that killed at least 40 people.

A powerful blast ripped through part of the Baksanskaya plant, Rushydro (HYDR.MM), Russia's largest hydroelectric power producer which runs the station, said in a statement.

Media quoted Emergencies Ministry workers as saying it took almost three hours to contain a fire that followed the blast.

"According to preliminary information, a terrorist act was the cause of the explosion and of the fire. Two guards died, two other people have been taken to hospital," Rushydro said.

Media quoted security sources as saying the two guards had been killed in a shootout with rebels.

Rushydro said power supplies to consumers had not been interrupted.

Baksanskaya is a relatively small power plant built in the 1930s during the Soviet Union's industrialisation drive. (Reporting by Dmitry Solovyov; Editing by Ralph Gowling)