According to a TASS report, a group of 10 Russian tourists and two guides set out on the trek on Tuesday. On Saturday, nine people started climbing the Klyuchevskaya Sopka volcano, while three remained in the camp at an altitude of 3,300 meters.
The victims climbing the volcano died at an altitude of about 4,150 meters. Rescuers onboard a helicopter are trying to extract the other climbers.
Details of the accident were not immediately known.
The Kamchatka peninsula is famous for its array of active and dormant volcanos, hot springs and abundant wildlife. Klyuchevskaya Sopka, with a height of about 4,750 meters, is the highest active volcano in Eurasia.