A Ukrainian drone struck a passenger bus in Starobeshevo in Russia’s Donetsk People’s Republic (DPR) on Saturday, injuring nine people, regional head Denis Pushilin said.

Pushilin added that a civilian truck driver was killed and six other people were injured in attacks on highways across the DPR throughout the day. Another man was injured in a drone strike in Makeevka, he said.

Four people were injured in Ukrainian drone attacks in Russia’s Belgorod Region. One of the victims was a 13-year-old boy who sustained shrapnel wounds while riding a bicycle, local emergency services said.

Ukraine has stepped up attacks on trucks and refineries in recent weeks, creating fuel shortages in Crimea and across western Russia. Strikes on the power grid have also caused blackouts on the Black Sea peninsula, which Ukraine claims as its own territory.

In many cases, the drones have targeted civilian trucks, cars, and buses. Last month, seven people were killed in a strike on a bus in the DPR.

Russian President Vladimir Putin said earlier this month that although the attacks on energy infrastructure had caused disruptions, they would not stop the advance of the Russian army on the front line. Last week, Russia captured Konstantinovka, one of the last strongholds held by Ukraine in the DPR.

Russian Deputy Prime Minister Aleksandr Novak said this week that the authorities would bolster air defenses and send additional fuel supplies to the regions hardest hit by the shortages.