Earlier in the day, emergency services told Sputnik that the group consisted of 12 people in total.
"The information is preliminary, very inaccurate, because connection is constantly lost. I was told that five people died, someone was wounded," Vasilevsky said.
Rescuers have been deployed to the scene, but are forced to scale part of the mountain on foot, the official said.
"The group is located at an altitude of 4,200 meters [13,780 feet], the helicopter cannot rise to that altitude. Rescuers have already arrived, they are now at an altitude of 3,300 meters," Vasilevsky said.
The Klyuchevskoy volcano, also referred to as Klyuchevskaya Sopka, is the highest mountain of Siberia and the highest active volcano of Eurasia at 4,754 meters.