Russia will abandon the rules of war, President Vladimir Putin's security council deputy has said, raising fears of nuclear strikes after Ukraine humiliated Moscow with a devastating attack on an oil refinery.

Suggesting the Kremlin's conflict could become even more brutal, Dmitry Medvedev - formerly Russian president and prime minister - said: 'It is time to openly declare that there are no longer, nor can there be, any rules regarding neo-Nazi Kyiv.'

This is due to 'the enemy's massive terrorist attacks on our cities,' said Putin's loyal lieutenant, as he hinted at the use of nuclear weapons in a future World War Three.

It comes after the Kremlin suffered an embarrassing blow this week when Ukraine launched a massive attack on a crucial oil refinery in Moscow. 

It was Ukraine's largest drone attack on the Russian capital in years, sparking fires in and around the Russian capital and forcing evacuations at the country's largest airport.

Footage captured the moment a Ukrainian drone struck the oil depot in the Kapotnya area of the city, sending a huge fireball into the sky as debris rained down around it.

Moscow residents complained of black rain falling from the sky following the attack, which authorities denied.

There were also fresh strikes from Russia overnight which struck Kharkiv, a city in the northeast of the country, with rescuers working for hours to rescue civilians from the rubble.

Russia has been accused of killing ordinary Ukrainians on a daily basis amidst the war.

Medvedev said: 'Only one thing must remain beyond the pale for us — the deliberate destruction of civilians.

'I emphasise "deliberate," meaning clearly intentional.

'Everything else is entirely permissible, no matter how much the degenerate from Bankova [meaning Zelensky] and his b****** European chorus line howl.'

He continued: 'This applies, incidentally, to the Hague Conventions on the laws and customs of war as well.

'They are no longer needed. Warfare has changed too much over the past century.

'Back then, it was considered unacceptable to steal from or kill the heads of even enemy nations.

'Moreover, missiles and drones have replaced the practice of dropping bombs from hot-air balloons. Thus, invoking the "rebus sic stantibus" clause is entirely appropriate here.'

This clause is an international law doctrine allowing a state to seek release from treaty obligations when a fundamental and unforeseen change in circumstances has radically altered the basis on which the agreement was made.

Medvedev, Putin's deputy on the Kremlin security council, did not specifically mention the Geneva Conventions - but implied Russia should not adhere to these, which include rules covering wounded and sick soldiers, prisoners of war, and protection of civilians.

Putin has been repeatedly accused of flouting the laws of war in its four-and-a-half year invasion of Ukraine, which has seen more than half a million people killed.

Medvedev also complained about Dutch discussions about potential WW3 detention facilities, which he characterised as 'concentration camps' for Russian prisoners.

'Some crazed Dutchmen - stoned out of their minds in their coffee shops - are musing about concentration camps for Russian prisoners of war,' he said.

'How should one respond to this drug-fuelled Dutch vomit?

'Unlike that vile old hag Europe - which has descended into neo-Nazism - Russia will not be creating concentration camps for Europeans.

'And not because it is immoral, but simply because, in the event of a war with some snot-nosed Dutchmen, such camps would be unnecessary.'

Threatening to use Moscow's nuclear arsenal he said: 'Radioactive bones and ash are usually buried deep in the ground.'

As Medvedev spoke, one man was killed in a strike in a two-story apartment building in Ukraine's second city Kharkiv.

Eight people were rescued from the rubble, including a six-year-old boy.

A day earlier an eight-year-old girl named Alina was killed in Pavlohrad.

Russian strikes have killed more than 790 children in the war.

On Monday, Russia's overnight barrage killed 11 people across Ukraine, including five in Kyiv and five in Kharkiv, and damaged the 11th-century Assumption Cathedral at the UNESCO-listed Kyiv-Pechersk Lavra.

Medvedev's fury was apparently ignited by the failure of Russia's air defences in Moscow on Thursday when the city's main oil refinery was struck and badly damaged by Ukrainian drones.

Ukraine insists that unlike Russia it targets solely military-linked targets and not civilians.

Following the strikes, Ukrainian President Volodymyr Zelensky said: 'We don't want this war, we never did, and everyone knows it, and our partners know it. But if Ukraine burns, your Moscow will burn.'

He held talks on Thursday in Brussels with Nato and European Union leaders, and the German and Ukrainian defense ministers signed an agreement to jointly develop an air defence system to counter ballistic missiles. 

The UN has verified roughly 16,000 civilian deaths in Ukraine since the full-scale invasion began in 2022, though the real figure is believed to be significantly higher.

Russia says about 7,000 civilians have been killed on its side of the conflict, but that figure is difficult to independently verify.