Russian President Vladimir Putin warned that Western nations' action in Ukraine would be greeted with a "lightning-quick" military response.

Putin's bellicose ultimatum came as Russia claimed responsibility for a missile strike in southern Ukraine that destroyed a "large batch" of Western-supplied weapons.

Countries assisting Ukraine "that have the audacity to meddle in ongoing events from the side and create untenable strategic threats for Russia" must understand that Russia's response to counterpunches will be lightning-fast, the Russian leader stated.

"We have all the tools that no one else has," Putin told St Petersburg legislators, alluding to Moscow's ballistic missile and nuclear arsenal.

"We're not going to brag about it; we're going to use them if necessary, and I want everyone to know that. We have already made all of the necessary judgments."

Russia's leader was not specific, but he recently oversaw the successful test of the Sarmat intercontinental ballistic missile, which Russia is expected to deploy shortly to carry ten or more nuclear warheads per missile.

'They believe it is perilous.'

Putin pledged to complete what he described as a "special military operation" to seize territory from Ukraine that Moscow historically considers being Russian. He accused NATO nations and their supporters of fomenting the conflict currently raging in Ukraine.

"Countries that have attempted to contain Russia in the past do not require a self-sufficient, massive country like ours. They believe it is hazardous simply by virtue of its presence. However, this is not the case. They are the ones who pose a threat to the entire world," Putin stated.

By initiating the offensive in Ukraine, Russian forces averted "a genuine danger of... a major conflict unfolding on our territory according to other people's scripts," Putin stated.

NATO, he claimed, intended to invade Russia via Ukraine, which Moscow seized in 2014, and the separatist-held eastern Donbas border region.

"All of the objectives of the special military operation we launched on February 24 in the Donbass and Ukraine will be unconditionally accomplished," Putin said, adding that Western attempts to "economically strangle Russia" through sanctions had failed.

'Small gains'

On Wednesday, fighting resumed in Ukraine's east along a relatively static front line measuring around 480 kilometers (300 miles). Russia claimed that its missiles struck a shipment of weaponry provided to Ukraine by the United States and European nations.

Speaking on the condition of anonymity to discuss intelligence findings, Western officials claimed Russia had made gradual headway in eastern Ukraine's Donbas region, capturing "minor gains" such as villages and small towns south of Izyum and on the outskirts of Rubizhne.

According to officials, the operation suffers from inadequate command, soldier and equipment losses, inclement weather, and robust Ukrainian resistance.

Russian forces have been transferred from the devastated southern port city of Mariupol to other areas of the Donbas. However, some residents stay in Mariupol to resist Ukrainian troops holed up at the Azovstal steel mill, the city's final stronghold. Around 1,000 people, together with an estimated 2,000 Ukrainian defenders, were seeking refuge there.

Just across the border in Russia, the governor said that a munitions dump in the Belgorod region caught fire Wednesday after numerous explosions were heard.

Additionally, explosions were reported in Russia's Kursk region near the Ukrainian border, while authorities in Russia's Voronezh region said that an air defense system shot down a droneult on energy supplies'

Polish and Bulgarian leaders accused Moscow of blackmailing their countries with natural gas after Russia's state-controlled energy corporation cut off supplies. European Union officials repeated those remarks and convened an emergency conference to discuss Russia's action.

According to Simone Tagliapietra, a senior fellow at the Bruegel think tank in Brussels, Russia's purpose in shutting down the gas supply is to "divide and rule" — pitting European countries against one another as they seek energy.

The shutdown and the Kremlin's warning that other countries could be targeted sent shivers of fear throughout the European Union's 27 member states.

Germany, the continent's largest economy, and Italy are two of Europe's leading consumers of Russian natural gas, though both have taken steps to minimize their reliance on Moscow.

"It's unsurprising that the Kremlin would attempt to blackmail us using fossil fuels," EU Commission President Ursula von der Leyen remarked.

"Today, the Kremlin's attempt to create dissension among member nations failed once more. The Russian fossil fuel age in Europe is drawing to a close."

Mateusz Morawiecki, Poland's prime minister, informed the Polish parliament that he believes Poland's backing for Ukraine and sanctions against Russia were the reasons for the gas stop. Bulgarian Prime Minister Kiril Petkov referred to the suspension as blackmail, adding, "We will not fall for such a con."

The International Energy Agency's executive director, Fatih Birol, described the stoppage as a "weaponization of energy supplies."

Europe does have some negotiating leverage in the conflict, as it pays Russia $400 million a day for gas, money Putin would lose if the supply were completely shut off.

Dmitry Peskov, Putin's spokesperson, claimed a Russian demand to pay for gas in roubles rather than euros or US dollars arose due to Western moves to freeze Russian hard currency assets.

He claimed that the West successfully "stole" those in an "unprecedented hostile action."