The Krasheninnikov volcano sent ash clouds up to 4 kilometres high, with footage showing stones and smoke rising from the crater in the Kronotsky Nature Reserve.
Local authorities said there are no residential areas nearby, and no immediate danger to people or infrastructure.
The eruption began Saturday night into Sunday and is believed to be linked to last week’s earthquake, centred about 120 kilometres from Petropavlovsk-Kamchatsky.
Scientists recorded several strong aftershocks, including one with a magnitude of 6.9. Emergency teams continue to monitor volcanic activity in the area.
