Russian strikes killed five civilians and wounded dozens in Ukraine, local officials said Saturday, after Russian President Vladimir Putin warned that sending European troops into Ukraine would amount to direct conflict with Russia.

Ukraine is under mounting pressure from Russia’s intensifying air campaign that uses ballistic missiles and jet-powered drones to pierce defenses. Moscow’s attacks have targeted Ukraine’s power grid ahead of winter in what officials say is meant to demoralize civilians.

Two people were killed and one wounded when Russian drones struck a residential area overnight in the Ukrainian city of Zaporizhzhia, regional head Ivan Fedorov said Saturday.

One person died and three others were wounded in strikes on Kryvyi Rih, according to local officials.

In the Black Sea port of Odesa and the surrounding area, 35 people were wounded overnight in what regional head Oleh Kiper called a “massive attack.” Among the buildings hit was a residential high-rise, whose upper floors were completely destroyed.