The Ukrainian attack over swathes of western Russia is just the latest in a series of escalating Russian and Ukrainian aerial strikes, targeting energy and military facilities over the nearly three-year war.

The assaults have escalated since Donald Trump won last year's US presidential election, with the Republican seeking a swift end to the fighting.

"The most terrible thing happened as a result of a drone attack on a residential house -- a two-year-old child and his mother were killed," Vyacheslav Gladkov, the governor of Russia's Belgorod border region said.

Another child and his father were also injured in the strike, he wrote on social media.

Russia's defence ministry said earlier it had downed 104 Ukrainian drones over western regions including Kursk and Bryansk, with smaller numbers intercepted over Smolensk, Tver, Belgorod and elsewhere.

Ukraine said one strike had hit an oil refinery in the town of Kstovo in Russia's Nizhny Novgorod region, around 800 kilometres (500 miles) from the front lines in eastern Ukraine.

Falling debris from a drone triggered a fire at the site, Russia said earlier.

- Refinery blaze -

"As a result of repelling a drone attack, debris fell on the Sibur-Kstovo enterprise causing a fire to break out," Sibur, a large petrochemical firm that owns the facility, said on Telegram.

Both Sibur and the regional governor said there were no casualties and firefighters were working to extinguish the blaze.

Images on social media -- not verified by AFP -- showed a huge blaze illuminating an urban skyline with flames and plumes of smoke rising over buildings.

Ukraine has previously said it is targeting Russian energy facilities to hamper military logistics and cut off revenues that fund the Kremlin's invasion effort.

The governor of Russia's Smolensk region, Vasily Anokhin, also said a Ukrainian drone "was shot down during an attempted attack on a nuclear power facility," adding there was no damage or casualties.

The governor did not specify which facility, but the Smolensk nuclear power plant is located near the town of Desnogorsk.

Ukraine said Russia had also launched an overnight drone attack of its own, resulting in air alerts in multiple Ukrainian regions and damage from debris in several.

The Ukrainian air force said it had downed 29 Russian drones over nine mainly southern and eastern regions.

In Kyiv, Mayor Vitali Klitschko said debris from a Russian drone had fallen in a central district of the capital.

And in the southern Black Sea region of Odesa, the governor said Russian drones had attacked port facilities in the town of Izmail.

In the southern city of Kherson, mayor Roman Mrochko said a 52-year-old man had been fatally wounded in a Russian drone attack.

The bombardments come at a critical juncture for Ukraine ahead of the third anniversary of the invasion, characterised by costly battles that have seen Russia make painstaking but steady gains, mainly in eastern Ukraine.

The Russian defence ministry said its advances were continuing Wednesday, announcing the capture of the village of Novoyelizavetivka in the industrial region of Donetsk.

It is one of four regions that Moscow claimed to have annexed into Russia in late 2022, despite not having full military control over any of them.

The settlement lies just across the border from the region of Dnipropetrovsk which Russian forces are nearing and look set to eventually enter for the first time of the war.

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