Russia's defeat in Ukraine could start a nuclear war, an ally of President Vladimir Putin has said in a warning to Nato.
The remarks came as the head of the Russian Orthodox Church said the world would end if the West tried to destroy Russia.
As Ukraine's allies meet to discuss supplying Kyiv with more weapons, the threat is intended to deter Nato from becoming even more involved in the war.
But the admission that Russia might lose on the battlefield marked a rare moment of public doubt from a prominent member of Mr Putin's inner circle.
“The defeat of a nuclear power in a conventional war may trigger a nuclear war,” Dmitry Medvedev, now deputy chairman of Mr Putin's powerful security council, said on Telegram on Thursday.
“Nuclear powers have never lost major conflicts on which their fate depends,” said Mr Medvedev, who was Russian president from 2008 to 2012.
Striking a similar tone at what he described as an anxious time for the country, Patriarch Kirill, the head of the Russian Orthodox Church, said in a sermon that trying to destroy Russia would mean the end of the world.
Drones and weapons supplied to Ukraine — in pictures
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Turkeysold its Bayraktar TB2 armed drones to Ukraine. They can fly at an altitude of 7,500 metres and swoop down to attack targets. AFP -
The US also gave 700 of its Switchblade kamikaze drones. AP -
Cheap commercial drones like the DJI Mavic series have been modified in Ukraine. AFP -
Germany will follow the US in providing a Patriot missile defence system, pictured above, to Ukraine. Reuters -
FIM-92 Stinger rockets have been donated to help Ukrainian infantry engage aircraft and drones. The shoulder-launched missiles can shoot down aircraft. Photo: US Army -
Germany donated 25 Flakpanzer Gepard all-weather-capable self-propelled anti-aircraft gun. AFP -
The High-Mobility Artillery Rocket System, or Himars, can simultaneously launch several precision-guided missiles. The US has given Ukraine projectiles with a range of about 130 kilometres. EPA -
M777 howitzers and about 300,000 shells have been donated to give Ukraine an accurate artillery platform with a range of 50 kilometres. EPA -
Ukraine has been sent at least 5,000 of the anti-tank weapons known as NLAWs. These shoulder-launched rockets have proved deadly in the field. PA -
Ukrainian troops have also received thousands of Javelin anti-tank missiles. Bloomberg -
Poland and the Czech Republic sent Russian-made T72 tanks, which Ukraine has used for decades, to ease integration and cut down training time. EPA -
France as announced its plan to give AMX-10 RC “scout tanks” to Ukraine. "This is the first time that western-made armoured vehicles are being delivered in support of the Ukrainian army," a French official said. AFP -
Shortly after the French, the US said it would send Bradley fighting vehicles to provide "a level of firepower and armour that would bring advantages on the battlefield”. Reuters -
The UK sent their phased-out Saxon armoured vehicles. They found new life protecting infantry units in transit and dealing with tough off-road conditions. Getty Images -
Denmark has supplied Harpoon anti-ship launchers to help Ukraine defend its coasts. AFP -
The US sent 20 Soviet and Russian made Mi-17 helicopters to Ukraine that had initially been bought for the Afghan government in 2010. AP -
Germany has also supplied its latest version of the IRIS-T air defence system designed to shoot down missiles at altitudes up to 20 kilometres. Getty Images -
Ukraine has also been given thousands of small arms, bullet proof vests, medical kits, litres of fuel, granades and other weapons systems. Reuters
“We pray to the Lord that he bring the madmen to reason and help them understand that any desire to destroy Russia will mean the end of the world,” state news agency RIA quoted him as saying.
“Today is an alarming time. But we believe that the Lord will not leave Russian land.”
Mr Medvedev said Nato and other defence leaders, due to meet at Ramstein Air Base in Germany on Friday to talk about strategy and support for Ukraine, should think about the risks of their policy.
Mr Putin has described Russia's “special military operation” in Ukraine as an existential battle with an "aggressive and arrogant West", and has said Moscow will use all available means to protect itself.
The Kremlin chief has sought in recent months to gird Russians for a much tougher battle while promising eventual victory in a war that the leaders of the West say they will never let him win.
Russia and Ukraine conflict latest — in pictures
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A tank, seen left, fires a round in Soledar, a town in the Donetsk region of eastern Ukraine. Reuters -
Tank fire in Soledar, Donetsk. Reuters -
Firefighters work to put out a blaze at a Kharkiv fireworks storage site after it was struck by a Russian missile. Getty -
Col Gen Oleksandr Syrskyi, commander of Ukraine's ground forces, visits his troops on the frontline in Soledar, Donetsk. Reuters -
A Ukrainian flag attached to a tank flutters in the wind in Bakhmut. Reuters -
A specialist from an emergency crew works on a residential building in Donetsk that was damaged in recent shelling. Reuters -
A missile fragment left by shelling in Russian-controlled Donetsk. AP -
Residents remove debris and carry their belongings out of a building destroyed by recent shelling in Donetsk, Russian-controlled Ukraine. Reuters -
Ukrainian forces fire an anti-aircraft weapon as Russia's attack on the frontline city of Bakhmut continues. Reuters -
A car drives past a destroyed building purported to have been used as temporary accommodation for Russian soldiers, dozens of whom were killed in a Ukrainian missile strike in Makiivka, Russian-controlled Ukraine. Reuters -
The site of a temporary barracks for Russian soldiers in Makiivka, which was destroyed in a Ukrainian missile attack. Reuters -
A Ukrainian serviceman carries his injured comrade from the battlefield to a hospital in the Donetsk region. AP -
Smoke rises after shelling in Soledar, the site of heavy battles with Russian forces in the Donetsk region. AP
The US has denied Russian claims that it wants to destroy Russia, while President Joe Biden has cautioned that a conflict between Russia and Nato could spark a Third World War.
But top Putin allies say the tens of billions of dollars' worth of US and European military assistance to Ukraine shows that Russia is now in a confrontation with Nato.
Russian Foreign Minister Sergey Lavrov said in Minsk that Moscow would do everything to ensure Nato and EU leaders “sobered up” as soon as possible.
Putin says world facing most dangerous decade since Second World War — video
Russia’s February 24 invasion of Ukraine has led to one of the deadliest European conflicts since the Second World War, and the biggest confrontation between Moscow and the West since the 1962 Cuban Missile Crisis.
The US and its allies have condemned the invasion as an imperial land grab while Ukraine has vowed to fight until the last Russian soldier is ejected from its territory.
Biden warns of nuclear 'Armageddon' — video
Since Russia invaded Ukraine, Mr Medvedev has repeatedly raised the threat of a nuclear war.
However, his admission now of the possibility of Russia's defeat indicates the level of Moscow's concern over increased western weapons deliveries to Ukraine.
Russia and the US, by far the largest nuclear powers, hold about 90 per cent of the world's nuclear warheads.
Asked if Mr Medvedev's remarks signified that Russia was escalating the crisis to a new level, Kremlin spokesman Dmitry Peskov said: “No, it absolutely does not mean that.”
He said Mr Medvedev's remarks were in full accordance with Russia's nuclear doctrine, which allows for a nuclear strike after “aggression against the Russian Federation with conventional weapons when the very existence of the state is threatened”.
