Vladimir Putin has ordered his military leaders to 'abandon the rules of war', Volodymyr Zelensky has claimed.

The Russian president has removed restrictions that had been in place for previous aerial bombardments, according to intelligence intercepted by Kyiv.

This order was issued in September, Ukraine's leader suggested, with Putin allegedly stating 'there are no rules now'.

His order coincided with Russia's increased assault on civilian infrastructure, including hospitals and schools, Mr Zelensky told the Financial Times. 

The Kremlin is now thought to be preparing to intensify its attacks on Ukraine's largest cities, including its capital Kyiv as well as Kharkiv, Odesa and Lviv.

Russia also reportedly intends to strike nuclear facilities to cut them from the energy grid. This would increase pressure on Ukraine to bow to Putin's demands.

Part of Moscow's plan is to force Ukrainians fleeing the violence to seek refuge in European countries, where anti-immigrant sentiment is growing, according to officials.

This is in response to Ukraine’s escalating strikes on Russian oil refineries, ports and warehouses, which have fuelled growing anger among civilians as shortages worsen and a heightened sense of insecurity takes hold. 

Meanwhile, Putin has warned that Russia could use 'all weapons' in its arsenal to respond to aggression from European countries. 

In remarks at a foreign policy forum, the Russian president accused the West and Europe of escalating tensions by talking about preparing for a war with Moscow in the coming years, conducting military drills in the Baltic Sea, and seizing Russian vessels.

His remarks followed Moscow's warning to NATO that it would not hesitate to use nuclear weapons to defend Kaliningrad should any members of the military alliance try to cut off the Baltic exclave from the rest of Russia.

Asked at the Valdai Club forum Thursday whether Russia was on the cusp of a war with NATO or whether both were trying to intimidate each other, Putin said: 'It's not intimidation, it's a response to an attempt to intimidate us.'

Putin said that 'everything is written correctly' in the earlier warning to NATO.

'If it comes to a direct attack on the Russian Federation - in this case we mean Kaliningrad, or maybe some other territories - of course, inevitably and immediately the question of [the] Russian Federation using all weapons at the disposal of our country will appear on the agenda,' he said.

Putin didn't specify whether Moscow would use nuclear weapons but said it has arms that 'no one else has' and would determine which to use in case of an attack.

Several Russian embassies in Europe this week issued statements that said Moscow has 'information that NATO is preparing (an) air and naval blockade of Kaliningrad and (the) Kaliningrad region.'

They accused European leaders of 'playing a dangerous game' by saying Russia might attack another country or ramp up a campaign of destabilizing attacks with drones and sabotage. Moscow has called the allegations absurd.

'There should be no mistake - Russia would be ready to use all its arsenal, including nuclear weapons, to defend its territory if NATO countries try to isolate [the] Kaliningrad region from the rest of the country,' the Russian Embassy in Ireland said in its statement on Tuesday.

NATO spokesperson Allison Hart confirmed Wednesday that Russia had sent a written message to the U.S.-led military alliance. 'We strongly denounce the threat of force, including any irresponsible nuclear rhetoric,' she said in a statement.

Hart insisted NATO is not targeting Kaliningrad and had sent a reply noting that 'NATO is a defensive alliance and none of our activities or exercises pose a risk to any part of Russia.'

NATO Secretary-General Mark Rutte said Wednesday the bloc's response to the message was 'short and concise.'

'Basically what we said is, `Hey, listen, we are a defensive alliance, and stop the nuclear threat. This is absolutely not called for and not helpful,'' Rutte told Euronews.

NATO's response also urged Russia to stop its 'unprovoked war of aggression against Ukraine,' now in its fifth year.

The Baltic exclave of Kaliningrad sits between NATO members Poland and Lithuania. It is home to Russia's main Baltic navy base and other military assets, and nuclear-capable Iskander missiles are deployed there.

Western military officers have said that key military installations in Kaliningrad would be a likely first target should Russia ever attack any NATO ally.

NATO allies have conducted military exercises in the Baltic Sea region in recent months. More are planned in October. It launched Operation Baltic Sentry there last year to protect communication cables and pipelines.

On August 18, NATO held an exercise over northern Poland and the Baltic region involving several aircraft, including an EA-37B Compass Call - a sophisticated American plane that can jam communications and radar, the U.S. Air Forces in Europe said.

Defense analysts believe the unannounced, large-scale exercise would not have been welcomed by the Kremlin.

European leaders and intelligence services have warned that Russia could be ready to strike at another country within a few years, especially if it wins its war on Ukraine.

Rutte told Euronews that Russia is trying 'to divide us and lose the focus' on defending Ukraine.

'We will not,' he said, adding that the best way to respond is to provide Kyiv with more support.

'That's the message. Calm, carry on, keep the support for Ukraine going. That's how we deal with it,' Rutte said.