Russia's state Tass news agency reported on Wednesday that Russia has started evacuating personnel from all of its diplomatic facilities in Ukraine.
Moscow has an embassy in Kyiv and consulates in Kharkiv, Odesa and Lviv.
The Tass report said the embassy in Kyiv confirmed the evacuations have begun. An Associated Press photographer in Kyiv saw the flag was no longer flying over the embassy building in Kyiv.
Ukraine also urged its citizens to leave Russia, and Europe braced for further confrontation on Wednesday after tensions escalated dramatically when Russia's leader received authorisation to use military force outside his country and the West responded with a raft of sanctions.
Hopes for a diplomatic way out of a new, potentially devastating war appeared all but sunk as the US and key European allies accused Moscow on Tuesday of crossing a red line in rolling over Ukraine's border into separatist regions — with some calling it an invasion.
The top US diplomat cancelled a meeting with his Russian counterpart; Kyiv recalled its ambassador and considered breaking all diplomatic ties with Moscow; dozens of nations further squeezed Russian oligarchs and banks out of international markets; Germany halted a lucrative pipeline deal; and the US repositioned additional troops to NATO's eastern flank bordering Russia.
After weeks of trying to project calm, Ukrainian authorities signalled increasing concern on Wednesday.
The Foreign Ministry advised against travel to Russia and recommended anyone there leave immediately, saying Moscow's “aggression” could lead to a significant reduction in consular services.
The head of Ukraine's National Security and Defense Council called for a nationwide state of emergency — subject to parliamentary approval.
Oleksiy Danilov said it will be up to regional authorities to determine which measures to apply, but they could include additional protection for public facilities, restrictions on traffic, and additional transport and document checks.
Already, the threat of war has shredded Ukraine's economy and raised the specter 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.
Russian President Vladimir Putin has yet to unleash the force of the 150,000 troops massed on three sides of Ukraine, while US President Joe 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.
German Foreign Minister Annalena Baerbock on Wednesday called European Union sanctions agreed a day before just “a first step” and also said further measures could follow.
Sanctions are key because the West has ruled out taking on Russia militarily.
Ukrainian Foreign Minister Dmytro Kuleba urged Western leaders not to wait.
“We call on partners to impose more sanctions on Russia now," he wrote on Twitter on Wednesday.
"Now the pressure needs to step up to stop Putin. Hit his economy and cronies. Hit more. Hit hard. Hit now.”
Responding defiantly to the steps already taken, Russian ambassador in the US Anatoly Antonov retorted that “sanctions cannot solve a thing” in a statement on Facebook.
“It is hard to imagine that there is a person in Washington who expects Russia to revise its foreign policy under a threat of restrictions.”
In Ukraine's east, where an eight-year conflict between Russia-backed rebels and Ukrainian forces has killed nearly 14,000 people, violence also spiked again.
One Ukrainian soldier was killed and six more sustained injuries after shelling by the rebels, Ukrainian military said.
Separatist officials reported several explosions on their territory overnight and three civilian deaths.
Since last Friday, when separatist leaders in the Donetsk and Luhansk regions announced mass evacuations into Russia, more than 96,000 residents of the separatist areas have crossed the Russian border.
After weeks of rising tensions, Putin took a series of steps this week that dramatically raised the stakes.
First, he recognised the independence of those separatist regions. Then, he said that recognition extends even to the large parts of the territories now held by Ukrainian forces, including the major Azov Sea port of Mariupol.
Finally, he asked for and was granted permission to use military force outside the country — effectively formalising a Russian military deployment to the rebel regions.
Still, Putin suggested there was a way out of the crisis, laying out three conditions: He called on Kyiv to recognize Russia's sovereignty over Crimea, the Black Sea peninsula that Moscow annexed from Ukraine in 2014, to renounce its bid to join NATO and partially demilitarise.
But it was unclear if there was actually any room for diplomacy since the first two demands had been previously rejected by Ukraine and the West as non-starters.
The Russian leader remained vague when asked whether he has sent any Russian troops into Ukraine and how far they could go, and separatist leader in Donetsk Denis Pushilin said Wednesday that there are currently no Russian troops in the region.
Pushilin's remarks contradict those of Vladislav Brig, a member of the separatist local council in Donetsk, who told reporters Tuesday that Russian troops had already moved in.
Late Monday, convoys of armoured vehicles were seen rolling across the separatist-controlled territories. It wasn't immediately clear if they were Russian.