From his post in Kyiv, Europe Editor James Mates gives a round up of Wednesday's developments
Russia's government has claimed rebel chiefs in eastern Ukraine have asked for military help to fend off Ukrainian “aggression”, although the US said this appeal is deception on Russia's part.
Fears of an imminent Russian offensive against its neighbor soared after President Vladimir Putin received authorisation to use military force outside his country, while the West responded with sanctions.
Kremlin spokesperson Dmitry Peskov said on Wednesday that rebel chiefs in Donestsk and Luhansk wrote to Russian President Vladimir Putin, telling him that shelling by the Ukrainian military has caused civilian deaths. An apparent photograph of the letter, shared by the Financial Times's Russia Correspondent, has Tuesday's date.
Western leaders, including Boris Johnson and Joe Biden, speculated last week that Russia would stage attacks as a pretext for an invasion of Ukraine. On Wednesday, White House spokesperson Jen Psaki said the announcement that separatists are seeking help ”is an example” of such an operation.
Ukraine's foreign minister Dmytro Kuleba pointed to another "example" - he said Wednesday's evacuation of a chemical plant in Crimea, annexed by Russia in 2014, was in preparation for a staged attack.
Both Russia and Ukraine have accused each other of atrocities.
Amid the volley of allegations, fears of a full-scale takeover continue to grow. According to Newsweek, US officials warned Ukraine on Wednesday evening that Russia will invade within the next 48 hours. Earlier in the day, invasion concerns led Ukraine to declare a nationwide state of emergency, lasting 30 days.
On Wednesday night, Ukrainian President Volodymyr Zelenskyy took to television to address the nation but appeared to believe there was little hope of a diplomatic breakthrough.
"Today, I initiated a phone conversation with the president of the Russian Federation," Mr Zelenskyy said.
"The result was silence. Although it's the Donbas where there should be silence."Ukraine's Foreign Minister Dmytro Kuleba urged the world on Wednesday to act against Russia immediately, or face "painful consequences".
Despite many western countries slapping sanctions on Russia's banks and billionaires, Mr Kuleba called for greater action. In a powerful speech at the UN General Assembly, the foreign minister said: “I warn every nation in this distinguished chamber, no one will be able to sit out this crisis if President Putin decides that he can move forward with his aggression against Ukraine. Your governments and people will face painful consequences."
Mobile and internet coverage in Ukraine's separatist areas dropped on Wednesday night, while several government websites were temporarily inactive following cyber attacks. It's the second tranche of attacks within eight days - on February 15, US and UK officials blamed Russia after government, military and major banking sites in Ukraine were brought down. Also on Wednesday, lawmakers in Ukraine approved President Zelenskyy's decree for a state of emergency. The measure - which allows authorities to impose curfews, block rallies and ban political parties and organisations - will cover all Ukrainian regions except Donetsk and Luhansk. The breakaway areas were declared independent states by Russia this week, before President Putin ordered "peace-keeping" troops into the regions.
The UK's sanctions for Russia have been criticised by MPs as "tepid". Emma Murphy outlines what US officials think of the PM's penalties
“For a long time we refrained from declaring a state of emergency... but today the situation has become more complicated,“ National Security and Defense Council head Oleksiy Danilov told the parliament, emphasising that Moscow’s efforts to destabilise Ukraine represented the main threat. Ukraine also urged its citizens to leave Russia immediately and advised against travel to the country, saying Moscow's “aggression” could lead to a significant reduction in consular services. Similarly, Russia evacuated its embassy in Kyiv, citing threats.
Wednesday was 'Defender of the Fatherland Day' in Russia, and to mark this occasion, President Putin released a video message, in which he called out the West. He said Russia's "appeals to build a system of equal and indivisible security" - that he claims would benefit all countries - remain "unanswered".
"We will continue to strengthen and modernise our army and navy, striving to increase their effectiveness, so they are fitted out with the most cutting-edge equipment," he added.
The US, the UK and European leaders had imposed sanctions on Russian banks and billionaires after President Putin ordered troops into Ukraine's Donetsk and Luhansk regions.
The European Union agreed to blacklist banks involved in financing separatist activities in eastern Ukraine and will ban EU investors from trading in Russian state bonds, according to Reuters.
The EU measures will "target the ability of the Russian state and government to access the EU's capital and financial markets and services, to limit the financing of escalatory and aggressive policies," a statement from the bloc said.
It also imposed sanctions on five people involved in a Russian parliamentary election in annexed Crimea in September 2021.
In the US, Secretary of State Antony Blinken cancelled plans for a Thursday meeting in Geneva with his Russian counterpart, saying Russia’s actions indicated it was not serious about a peaceful path to resolving the crisis.
Correspondent Dan Rivers reports that internet coverage has cut out in Bakhmut, a city close to the border of Ukraine's breakaway region
President Joe Biden said Moscow had flagrantly violated international law by invading Ukraine and that "none of us will be fooled” by the Kremlin's intentions.
Alongside sanctions, Mr Biden said he was moving additional US troops and attack aircraft to Nato's Baltic allies as a show of support, though he described the deployments as purely “defensive,” adding: “We have no intention of fighting Russia.”
Boris Johnson announced on Tuesday that three billionaire allies of the Russian president and five Russian banks would face punitive measures from the UK. But Mr Johnson faced criticism from all political sides for not going far enough with efforts described as "tepid".
In perhaps the most significant intervention, German Chancellor Olaf Scholz took the step of blocking the certification of the Nord Stream 2 pipeline that would have supplied gas directly from Russia to Germany.
Despite these widespread sanctions, former Nato head Anders Fogh Rasmussen said the West should've been tough on years ago.
Mr Rasmussen, who was secretary general from 2009 to 2014, told ITV's Peston show: "It was a mistake not to react more strongly after the 2014 aggression against Ukraine, when [Mr Putin] took Crimea."
He said that now, direct military action from Nato against President Putin's troops can't be ruled out.
"I think his primary goal would be to capture all of Ukraine and annex it into the Russian Federation," Mr Rasmussen added.
"If he can't achieve that, I think he would occupy the whole of eastern Ukraine and use that as a tool to prevent Ukraine from acceding to NATO and also the European Union."
Already, the threat of war has shredded Ukraine’s economy and raised the spectre of massive casualties, energy shortages across Europe and global economic chaos.
Even as the conflict took a new, dangerous turn, leaders warned it could still get worse. Putin has yet to unleash the force of the 150,000 troops massed on three sides of Ukraine, while Biden held back on even tougher sanctions that could cause economic turmoil for Russia but said they would go ahead if there is further aggression.