Russia’s widespread overnight attack targeting critical energy infrastructure facilities in Ukraine was a response to strikes on Russian territory using US-made ATACMS missiles, President Vladimir Putin said Thursday.

Putin claimed Russia hit 17 targets that were “military facilities, defense industry facilities and their support systems,” without acknowledging the hits to power infrastructure. “As I have said many times, there will always be a response from our side (to the use of American ATACMS),” Putin said during comments made at a security summit in Kazakhstan.

More than a million households in Ukraine were left without power following the aerial bombardment, authorities in the country said. This is Russia’s 11th large-scale assault on Ukraine’s energy supplies this year alone, according to the energy ministry in Kyiv, a strategy that has caused nationwide rolling blackouts.