At least 13 people were killed in a Ukrainian drone strike on Russia’s Tatarstan region Monday, marking one of Kyiv’s deadliest attacks since the war began four years ago.

Kyiv said it had struck an oil refinery in the industrial city of Nizhnekamsk, more than 1,000 kilometers (620 miles) away from the Ukrainian border.

Both sides have significantly escalated their long-range attacks this year, causing a spike in civilian deaths, according to the United Nations.

"At this moment, 13 people have been killed" in the attack on Nizhnekamsk, the regional press service said in a statement Monday.

Another 75 people were wounded, 21 of whom had been hospitalized, the authorities added.

Russia's Tatarstan region is rich in energy resources and has many major oil refineries that Kyiv has been targeting in retaliatory strikes.

Unverified footage on social media showed a large black smoke cloud billowing at the site of an oil facility.

Ukraine's General Staff said it had struck the Taneko refinery, controlled by oil giant Tatneft, as part of a campaign of "reducing the military potential of the Russian aggressor."

Russia's Investigative Committee, which probes major crimes, said a child was among those killed.

So too were citizens from Tajikistan and Uzbekistan, according to the regional government.

Deadly strikes

Russia also hit Ukraine with deadly strikes Monday.

Near the front line, a Russian artillery strike killed five people in a village in the northeastern Kharkiv region, local Ukrainian officials said.

"On Aug. 10, Russian forces carried out a massive artillery strike on the residential area of the village of Bugaivka in the Chuguiv district. Various houses were destroyed as a result of the enemy attack. Five people were killed," the regional prosecutor's office said in a statement on Telegram.

It posted a picture of a house reduced to rubble by the attack.

Russia's Defense Ministry said it shot down 456 Ukrainian drones fired overnight. It never states how many reached their targets.

The Tatarstan region had earlier reported a "massive" Ukrainian drone attack.

Ukraine's air force said Russia fired 126 drones in its overnight attack.

A woman was also killed in a Ukrainian attack on the Russian border region of Belgorod and a man was killed in a Russian drone strike on a taxi in the frontline Kherson region, officials there said.

In Ukraine's southern Odesa region, tens of thousands of households were still without power after Russia struck the power grid over the weekend.

Concerns are rising in Kyiv over the upcoming winter, with the energy network still reeling from four years of Russian strikes.

Last winter, millions were plunged into darkness and had their heating and water cut for hours as temperatures sank to minus 20 degrees Celsius (-4 degrees Fahrenheit).

Ukrainian President Volodymyr Zelenskyy warned on the weekend that his country has "virtually no intact thermal power plants" following the Russian attacks.

Kyiv has also been running short of vital missile interceptors as Russia has significantly escalated its attacks with hard-to-intercept ballistic missiles.

Dozens have been killed in Kyiv over the last two months in direct hits on apartment buildings.