Ukrainian drones attacked a military air base in western Russia in a long-range strike aimed at curbing Moscow’s ability to hit its territory with guided bombs.

Six jets were destroyed and another eight significantly damaged in the attack on an airfield near Morozovsk in Russia’s Rostov region situated nearly 186 miles away from Ukraine-controlled territories, according to a Ukrainian person familiar with the joint operation by the country’s security service, SBU, and its military. About 20 Russian servicemen were killed or wounded, the person said, asking not to be identified as the matter is sensitive.

The Russian Defense Ministry said it downed 53 Ukrainian drones overnight including 44 in the Rostov region, without elaborating on any damage. The drones were targeting Morozovsk district, which hosts the airbase, regional governor Vasily Golubev said on Telegram. The attack damaged a power substation in the area, temporarily leaving 600 residents without electricity.

Later on Friday, Golubev said, eight Russian investigators at the site near Morozovsk airfield were injured after an explosive device on a downed drone detonated.

The pro-Moscow military blogger Rybar, which has more than 1.2 million subscribers on Telegram, posted about the airbase attack, but said no jets were damaged. Aside from Morozovsk, Russian air defense also downed Ukrainian drones headed toward airbases in Yeysk, Krasnodar region, and Engels, Saratov region, Rybar said.

Ukraine has been trying to offset its lack of air force and long-range weapons by using explosive-laden drones, reaching ever further into Russia. Refineries and airfields used by President Vladimir Putin’s air force have been frequent targets, though other industrial and military sites have been struck as well.

While Russia has made regular use of guided bombs against Ukraine’s frontline troops, it also recently stepped up attacks with the highly destructive weapon against the country’s second-largest city, Kharkiv.