Russia will use all weapons at its disposal against Ukraine if it was to acquire nuclear arms, President Vladimir Putin warned on Thursday, also threatening to use new hypersonic missile to attack "decision-making centers" in response to Kyiv's firing of Western missiles.

Some unidentified Western officials had suggested U.S. President Joe Biden could give Ukraine nuclear weapons before he leaves office, the New York Times reported last week.

"If the country which we are essentially at war with now becomes a nuclear power, what do we do? In this case, we will use all; I want to emphasize this, precisely all means of destruction available to Russia. Everything: we will not allow it. We'll be watching their every move", Putin said during a press conference in Astana, Kazakhstan.

"If officially someone were to transfer something, then that would mean a violation of all the non-proliferation commitments they have made," he added.

Putin also said it was practically impossible for Ukraine to produce a nuclear weapon, but that it might be able to make some kind of "dirty bomb," a conventional bomb laced with radioactive material in order to spread contamination. In that case, Russia would respond appropriately, he said.

Russia has repeatedly said, without providing evidence, that Ukraine might use such a device.

Ukraine inherited nuclear weapons from the Soviet Union after its 1991 collapse, but gave them up under a 1994 agreement, the Budapest Memorandum, in return for security assurances from Russia, the United States and Britain.

Ukrainian President Volodymyr Zelenskyy has repeatedly complained that the move left his country without security, citing this as a reason it should be admitted to NATO – something Moscow strongly opposes.

Hypersonic missile threat

Putin also said Russia could fire its new Oreshnik hypersonic missile at the Ukrainian capital Kyiv in response to Ukraine's strikes on its territory.

The threat comes a week after Russia used the experimental weapon for the first time against the Ukrainian city of Dnipro, in a major escalation of the almost three-year war.

"We do not rule out the use of Oreshnik against the military, military-industrial facilities or decision-making centers, including in Kyiv," Putin said.

"Authorities in Kyiv today continue their attempts to strike at our vital facilities, including in Saint Petersburg and Moscow," he added.

The intermediate-range ballistic missile can travel at a speed of Mach 10, or up to three kilometers (1.8 miles) per second, according to Moscow.

Putin said the weapon had the destructive power of a meteorite.

"The kinetic impact is powerful, like a meteorite falling. We know in history what meteorites have fallen where, and what the consequences were. Sometimes it was enough for whole lakes to form," he said.

The weapon is "comparable in strength to a nuclear strike" when used several times at once, the Kremlin chief added, though he said it was not currently equipped with a nuclear device.

Second big attack on energy sites

Meanwhile, Russia triggered deep power cuts across Ukraine as it unleashed its second big attack on Ukraine's energy infrastructure this month on Thursday.

Putin said Moscow had struck in response to Ukraine's strikes on Russian territory with U.S. medium-range ATACMS missiles.

Zelenskyy accused Russia of a "despicable escalation," saying it had used cruise missiles with cluster munitions.

Over 1 million people lost power in the immediate aftermath of the strikes, and millions more had their existing schedule of rolling power cuts intensified.

Ukraine's Air Force said Russia used 91 missiles and 97 drones in Thursday's attack. It said 12 of those had hit their targets, most of which were energy and fuel facilities.

"The enemy is using a large number of missiles and drones. Their massive use in certain areas often exceeds the number of means of (air defense) cover," the Air Force said in a statement.

Infrastructure facilities were damaged in nine regions, Ukraine's Interior Ministry said.

The attack reinforced fears of long power cuts during the winter months as temperatures hover around zero.

Officials said it was the 11th major strike on the energy system since March. Russia has knocked out about half of Ukraine's available generating capacity during the war, damaged the distribution system and forced authorities to impose long blackouts.

The Air Force said it had shot down 79 missiles and downed 35 drones, while 62 drones were "lost," meaning it was likely they had been disrupted by electronic warfare.

A source in the energy sector said Ukraine had disconnected all nuclear power units from the grid before the attack to protect them. Ukraine gets more than half of its electricity from nuclear plants.

Ukraine's state grid operator, Ukrenergo, announced deep power cuts across the country because of damage from the attacks, warning of at least 12 hours without electricity for some consumers.

All missiles or drones aimed at the capital, Kyiv, were brought down, officials said.

Thermal and radar decoys

The Air Force said Russia was using thermal and radar decoys to trick Ukrainian air defenses and putting electronic warfare devices on its missiles.

"All this significantly complicates the operation of Soviet-made anti-aircraft missile systems... Western systems work much more effectively in such conditions, but Ukraine does not have enough to reliably cover hundreds of critical infrastructure facilities," it said.

It said foggy weather conditions also made it harder for machine gunners to spot drones.

More than 33 months after Russia invaded Ukraine, Russian ground forces are advancing at their fastest pace in two years.

Russia fired a new hypersonic intermediate-range ballistic missile at Ukraine this month after the United States allowed Kyiv to strike Russian territory with advanced Western missiles.

"Putin does not want peace. We must force him into peace through strength," Foreign Minister Andrii Sybiha said, reiterating Kyiv's call for more air defense and long-range capabilities from Western allies.

In western Ukraine, Lviv regional governor Maksym Kozytskyi said Thursday's Russian strikes had cut off electricity to about 523,000 people. Power was also cut to nearly 500,000 people in the Volyn and Rivne regions, their governors said, and disrupted in the Khmelnytskyi and Zhytomyr regions.

State oil and gas firm Naftogaz said its facilities had been attacked in the morning airstrikes.

Officials across Ukraine said they were turning on generators to ensure emergency heat and water supplies to hospitals, schools and other critical facilities during bitter winter weather.