Ukraine is set to introduce emergency measures and told its citizens in Russia to flee the country as fears of a large-scale invasion mount.
In another ominous sign, Moscow began evacuating its Kyiv embassy.
It came as US military officials at the Pentagon said Russian forces are “as ready as they can be” to mount an invasion, with about 80% in attack positions.
“He is as ready as he can be. We’ve been saying any day now and it’s certainly possible that today is that day,” a US official said.
Key developments:
• European Union sanctions against Russia have come into effect
• Ukrainian government and banking websites have been knocked offline
• White House says Biden-Putin summit ‘not in the plans’ anymore
• UN secretary general warns against the risks of an expanded conflict
State of emergency
In Ukraine, the state of emergency could restrict the freedom of movement of conscripted reservists, according to a draft text reported by the Reuters news agency and still awaiting parliamentary approval.
It could also see curbs imposed on the media and lead to personal document checks.
The restrictions would come into force from Thursday. They would last 30 days and could be extended for another 30 days.
Army reservists aged 18-60 are also being conscripted following a decree by Ukrainian President Volodymyr Zelenskyy.
Civilians will be given the right to carry firearms and defend themselves after the country’s parliament voted in favour of the measure.
‘Hit more. Hit hard. Hit now’
At a UN General Assembly meeting, Ukraine urged nations to stop Russia’s “aggressive plans” and called for harsher sanctions, a day after the UK, the US and the EU announced a first wave of measures targeting Russia.
“No one will be able to sit out this crisis if President Putin decides that he can move forward,” Ukraine’s Foreign Minister Dmytro Kuleba said.
He urged Western leaders not to wait, saying: “We are at a critical juncture of world history, and our actions today define it for years to come.”
“We call on partners to impose more sanctions on Russia now,” he tweeted.
“Now the pressure needs to step up to stop Putin. Hit his economy and cronies. Hit more. Hit hard. Hit now.”
Putin: National interest comes first
Earlier, President Vladimir Putin said Russia was still open to diplomacy but would put its national security interests first.
He said the country would continue to bolster its military amid a “difficult international situation”.
In a video statement released to commemorate the annual Defender of the Fatherland Day, Mr Putin appeared to indirectly address the situation in Ukraine despite making no specific mention of the country.
“Our country is always open to a direct and honest dialogue and ready to search for diplomatic solutions to the most complicated issues,” Mr Putin said.
“But I want to repeat that Russia’s interests and the security of our people are unconditional.
“So, we will continue to strengthen and modernise our army and navy.”
Russia targeted by sanctions
Russia is being targeted by sanctions from countries like the US and UK after Mr Putin declared that he recognised the independence of two separatist-held areas in eastern Ukraine and sent in troops.
“We can see the difficult international situation and the threats posed by current challenges, such as the erosion of the arms control system and NATO’s military activities,” Mr Putin said.
“And yet, Russia’s appeals to build a system based on equal and indivisible security that would reliably defend all countries, remain unanswered.”
Russia’s security service said it has foiled “an act of terrorism” in Crimea, the Ukrainian territory Russia annexed in 2014, according to the state-owned RIA news agency.
Six Russian citizens were arrested who were allegedly supporters of a Ukrainian extremist group, the news outlet said.
Read more: What will happen if Vladimir Putin chooses all-out war?
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