A far-left activist group took credit on Sunday for an attack on a gas-fired power plant at Berlin that caused power outages for nearly 50,000 households and more than 2,000 businesses a day earlier.

It could be several days before power is restored to all customers as the city deals with freezing temperatures and snow.

Calling themselves the Volcanic Group, the culprits claim that power outages were not the goal of their action but say the intended target was the fossil fuel industry.

The group posted a letter online claiming responsibility for the incident. The group claims it set fire to a cable bridge carrying high-voltage power lines and short-circuited the charred cable strands with steel bars lying around the site.

Volcanic Group claim the attack was intended to cause power outages only in the “wealthier districts” of Berlin.

“We apologize to the less affluent residents of southwest Berlin,” the group said in a statement.  “Our sympathy for the many villa owners in these districts is limited.”

The group tried to portray the attack as self defense. “Entire regions are rendered uninhabitable by the heat. They simply burn up,” the group claimed. “Or habitats disappear beneath the waves during floods or due to rising sea levels.”

Authorities were not sympathetic to the group’s rationale.

“Suspected left-wing extremists knowingly endangered human lives with this attack,” Berlin’s mayor, Kai Wegner, said in an X post. “Particularly those of patients in hospitals as well as of elderly people, children, and families.”

Mr. Wegner said electricity and heat must be secured as quickly as possible and promised a thorough investigation of the perpetrators.

The head of Berlin State Politics Office, Christian Latz, said on X that two people with high care levels, including an elderly man confined to a wheelchair, had to spend the night in a gymnasium because their power was out.

The power company, Stromnetz Berlin, said in a message on its website that about 10,000 households and 300 businesses now have their power back on but the restoration of the supply of electricity for more than 30,000 other customers would not take place until Thursday afternoon.

The Senator of the Interior, Iris Spranger, declared a major damage situation to make it easier to mobilize support forces.

“The claim of responsibility has been classified as authentic by the security authorities,” Ms. Spranger said in a statement. “I condemn this contemptible attack on the women, men, and guests of Berlin in the strongest possible terms. The investigations are ongoing.”

Left-wing extremists cause millions of euros in damage a year in attacks on critical infrastructure and businesses, according to Germany’s intelligence services. An online report claims  that similar “volcano groups” have carried out attacks at irregular intervals since 2011.

They say the unknown perpetrators connected to the movement carried out an attack on the Mörsch Bridge in Berlin in 2018, setting fire to vital utility lines. The heat damaged parts of the bridge so severely that there was a risk of collapse.

More recently, a group calling itself Shut Down Tesla Volcano claimed responsibility for an arson attack on a power pole on March 5, 2024, near a Tesla Gigafactory that interrupted the power supply to a Tesla plant near Berlin, resulting in a prolonged production outage.