Ukraine launched overnight drone attacks on three oil refineries deep inside Russia, a Ukrainian defense source told CNN on Wednesday, as Kyiv intensifies its cross-border strikes days before President Vladimir Putin’s anticipated re-election.

The source told CNN that Ukraine is “implementing a well-planned strategy to decrease Russian economic potential.”

The three Russian oil refineries targeted are in the cities of Ryazan, about 130 miles southeast of Moscow; Kstovo, in the Nizhny Novgorod region, nearly 300 miles east of the capital; and Kirishi in Russia’s northwest. The trio of facilities are among Russia’s largest refineries, the source said.

It marked the second consecutive day of Ukrainian attacks on Russian energy sites, and the locations targeted represent a spate of attacks well within Russia’s territory.

“Our goal is to take away our enemy’s resources and decrease the flow of oil money and fuel Russia is using directly on the war,” the source told CNN.

They came after a chaotic day on the Russian side of the Ukrainian border, during which pro-Ukrainian groups of Russian fighters said they launched cross-border attacks and claimed to have gained control of the village of Tyotkino in Russia’s Kursk region.

The fallout from the attack continued into Wednesday. The Freedom for Russia Legion, a group of Russian dissidents fighting for Ukraine which has previously claimed responsibility for incursions into Russia, said in a series of posts on Telegram on Wednesday that its fighters had destroyed a command center in the village of Tyotkino in the Kursk region, and were advancing further.

CNN cannot independently verify the group’s claims. However, CNN was able to geolocate video footage posted by the group that shows a building engulfed in smoke and flames that was located in Tyotkino.

“There was a control center and there is no control center,” the group said. “We are bringing a crisis to the bloody regime’s defense industry closer.”

Strikes come as Russia’s election nears

Russia’s defense ministry said Wednesday its air defenses destroyed 58 Ukrainian drones overnight, including some that traveled as far as the Leningrad region, which borders Finland, supporting Kyiv’s claims.

The regional governor in Ryazan, Pavel Malkov, said a fire broke out at the facility there but has since been extinguished. He said two people were injured.

Social media video from the refinery complex, one of Russia’s largest, showed a large plume of smoke billowing from a building in the distance.

A day earlier, Russian authorities reported at least 25 drone attacks, with local officials in the Oryol and Nizhny Novgorod regions reporting hits to fuel and energy facilities.

No casualties have been reported from either Tuesday or Wednesday’s attacks.

But an apparent cross-border incursion on Tuesday saw attacks launched in the village of Odnorobovka in Ukraine’s Kharkiv region, and in the nearby Russian villages of Nekhoteevka and Spodariushino in Belgorod, according to Russian authorities.

Russia’s Belgorod Region Governor Vyacheslav Gladkov said 10 civilians were injured and six were hospitalized in the region on Tuesday.

As well as targeting Russia’s deep oil reserves, Kyiv’s latest strikes may be partially intended to bring home to Russians the impact of the war just as the country prepares for a presidential election.

The vote is essentially certain to hand Putin a fifth term, extending his rule into the 2030s. Voting will take place over three days from Friday, with the president sailing towards another spell in power in a ballot that is not considered free or fair and in which he faces no genuine competition.

During a lengthy interview on state television channel Rossiya 1 on Wednesday, Putin said Ukrainian attacks on Belgorod and Kursk are happening amid Kyiv’s “failures” on the battlefield.

“All this is happening against the backdrop of failures on the line of contact, on the front line. They did not achieve any of the goals they set for themselves last year,” Putin said. “Against the backdrop of those failures, they need to show at least something, and, mainly, attention should be focused on the information side of the matter.”