KYIV, Ukraine - Ukrainian President Volodymyr Zelensky said Thursday that Russia could start "a major war in Europe" in the coming days and urged Russians to oppose the attack.
In an address aired shortly after midnight Zelensky said Russia could invade Ukraine "any day now" and, addressing the Russian people, said whether that happens "depends on you."
"Who can stop (the war)? People. These people are among you, I am sure," he said.
Zelensky said he had tried to call Russian President Vladimir Putin but there was "no answer, only silence", adding that Moscow now had around 200,000 soldiers near Ukraine's borders.
Rebel leaders in eastern Ukraine have asked Moscow for military help against Kyiv, the Kremlin announced late Wednesday, in a move that opens the door for massed Russian troops to move in.
Separatist leaders of Donetsk and Lugansk sent separate letters to Putin, asking him to "help them repel Ukraine's aggression," Putin's spokesman Dmitry Peskov said.
The two letters were published by Russian state media and were both dated February 22.
Their appeals came after Putin recognized their independence and signed friendship treaties with them that include defense deals.
Tens of thousands of Russian troops are stationed near Ukraine's borders, with the West saying they could be used for an attack at any moment.
On Tuesday, Russian lawmakers gave Putin permission to use force abroad, while the next day Ukraine mobilized reservists as eastern Europe slid ever closer towards a potentially catastrophic conflict.
Ukraine's parliament has also imposed a state of emergency giving regional authorities and emergency services sweeping powers to step-up controls including ID checks and roadblocks.
'Moment of peril'
Putin has defied a barrage of international criticism over the crisis, with some Western leaders saying he was no longer rational.
Western diplomatic efforts to halt the march to war have so far proved fruitless, but European Union leaders announced one more last-ditch summit in Brussels on Thursday to address the crisis.
United Nations Secretary-General Antonio Guterres warned the body that "our world is facing a moment of peril" and that "the world could see a scale and severity of need unseen for many years".
The US ambassador to the United Nations, Linda Thomas-Greenfield, warned that an all-out Russian invasion could displace five million people, triggering a new European refugee crisis.
Ukraine also urged its approximately three million citizens living in Russia to leave.
"We are united in believing that the future of European security is being decided right now, here in our home, in Ukraine," Ukrainian President Volodymyr Zelensky said during a joint media appearance with the visiting leaders of Poland and Lithuania.
"Ukraine needs security guarantees. Clear, specific, and immediate," Zelensky said, adding: "I believe that Russia must be among those countries giving clear security guarantees."
Western capitals say Russia has amassed 150,000 troops in combat formations on Ukraine's borders with Russia, Belarus and Russian-occupied Crimea and on warships in the Black Sea.
Ukraine has around 200,000 military personnel and Wednesday's call up could see up to 250,000 reservists aged between 18 and 60 receive their mobilisation papers.
Moscow's total forces are much larger -- around a million active-duty personnel -- and have been modernised and re-armed in recent years.
High cost of war
But Ukraine has received advanced anti-tank weapons and some drones from NATO members. More have been promised as the allies try to deter a Russian attack or at least make it costly.
Shelling has intensified in recent days between Ukrainian forces and Russia-backed separatists -- a Ukrainian soldier was killed on Wednesday, the sixth in four days -- and civilians living near the front are fearful.
Dmitry Maksimenko, a 27-year-old coal miner from government-held Krasnogorivka, told AFP that he was shocked when his wife came to tell him that Putin had recognised the two Russian-backed separatist enclaves.
"She said: 'Have you heard the news?'. How could I have known? There's no electricity, never mind internet. I don't know what is going to happen next, but to be honest, I'm afraid," he said.
In a Russian village around 50 kilometres (30 miles) from the border, AFP reporters saw military equipment including rocket launchers, howitzers and fuel tanks mounted on trains stretching for hundreds of metres.
Washington and Britain say Russia's force is poised to strike Ukraine and trigger the most serious war in Europe for decades, but Putin says he is open to negotiation -- within limits.
Russia has demanded that Ukraine be forbidden from ever joining the NATO alliance and that US troops pull out from Eastern Europe.
On Tuesday, the Federation Council, Russia's upper house, gave him unanimous approval to deploy troops to the two breakaway Ukrainian regions.
Russia said it had established diplomatic relations "at the level of embassies" with the separatist statelets, which broke away from Kyiv in 2014 in a conflict that has cost more than 14,000 lives.
Moscow also said it would evacuate diplomatic personnel from Ukraine to "protect their lives".
Speaking to journalists, Putin on Tuesday set out a number of stringent conditions if the West wanted to de-escalate the crisis, saying Ukraine should drop its NATO ambition and become neutral.
Washington Wednesday announced sanctions on the Nord Stream 2 gas pipeline, which Germany had earlier effectively suspended by halting certification.
The Russian foreign ministry has said it is preparing a "strong response" to US sanctions.
Australia, Britain, Japan and the European Union have all also announced sanctions.
© Agence France-Presse