German federal prosecutors on Tuesday launched a terrorism investigation into an arson attack on high-voltage cables that caused a power blackout affecting 45,000 Berlin households.

The service said it was probing Saturday's attack – claimed by a far-left extremist group – on charges including "membership in a terrorist organisation, sabotage, arson and disruption of public services".

The arson attack was claimed online by a left-wing extremist group that calls itself Vulkangruppe (Volcano Group) and said it was targeting "the fossil fuel economy" driving climate change.

"In the greed for energy, the Earth is being drained, sucked dry, burned, ravaged, razed, raped and destroyed," part of the letter stated.

Berlin's Mayor Kai Wegner condemned the attack, saying that "suspected left-wing extremists knowingly put lives at risk, especially those of patients in hospitals, as well as the elderly, children and families".

On Tuesday, approximately 24,700 households and 1,120 businesses were still affected. The grid operator, Stromnetz Berlin, said it aims to restore full power supply by Thursday afternoon.

The Volcano Group has previously said it was behind an act of sabotage at a Tesla factory in which power lines supplying the site were set on fire.

According to domestic intelligence service BfV, the group has existed since 2011 and has been carrying out arson attacks in Berlin and the surrounding state of Brandenburg ever since. Their targets are usually cable ducts along railway lines, radio masts or power supply systems.

The German capital also suffered a major power outage affecting tens of thousands of residents in September after a blaze hit electricity pylons.

Police likewise suspected arson in that case, and an unnamed anarchist group claimed responsibility online for starting the blaze.

Germany has been on high alert for sabotage activities directed at its infrastructure, including from foreign actors such as Russia. (AFP)