"Deep gratitude to the volunteers, rescuers, and residents of the Sobolevsky District," Sergei Lebedev, the regional minister for emergency situations, was quoted by RIA Novosti as saying, Xinhua news agency reported.

The whale was found on Thursday dehydrated, with cracked skin and several injuries. Rescuers transported it by truck to a nearby river mouth, where it was released.

This is the second killer whale rescue operation in the region in recent weeks, following the release of a whale family, including calves, in October.