Global efforts to head off a Russian invasion of Ukraine have been dealt a serious blow.
Russian President Vladimir Putin has signed decrees recognising the independence of two separatist regions in eastern Ukraine and ordered his military to "maintain peace" in the disputed areas.
Mr Putin's moves — made as shelling continued in those areas — could be a precursor to the Kremlin sending troops and weapons into Ukraine to support the Russian-backed separatists.
Officials from the US, UK, EU and Australia have called it a breach of international law and several governments have vowed to retaliate with economic sanctions.
So, what might Russia do next?
And how have Ukrainians responded to what some have deemed a "declaration of war" by Mr Putin?
What might Russia do next?
In a lengthy address, Mr Putin outlined his justification for ordering the deployment of troops to "keep the peace" in the breakaway Donetsk and Luhansk regions — known collectively as Donbas — which he recognised as independent republics and thus not part of Ukraine.
Sweeping through more than a century of history, he painted today's Ukraine as a modern construct that is inextricably linked to Russia.
Mr Putin charged that Ukraine had inherited Russia's historic lands and after the Soviet collapse was used by the West to contain Russia.
Max Seddon, the Financial Times newspaper's Moscow bureau chief, deemed Mr Putin's address a "war speech" that was "downright scary".
"This is only the beginning. The speech made it clear: war's on the table," he said on Twitter.
Moscow's recognition of the rebel-held territories' independence effectively shatters a 2015 peace deal for eastern Ukraine, known as the Minsk agreement.
Pjtor Sauer, a reporter for the Moscow Times, told the ABC it was a "huge escalation" in the conflict.
"It's a huge escalation of the current situation."
While the exact nature of the "peacekeeping" force Mr Putin plans to deploy remains unclear, the decree said Moscow could now build military bases in Donetsk and Luhansk.
Moscow and the separatists also vowed to defend each other and sign separate agreements on military cooperation.
Reuters later reported large numbers of military vehicles and hardware are moving through Donetsk, the largest city in one of the two self-proclaimed republics.
While the UN Security Council is set to hold an emergency meeting at the request of Ukraine, Gorana Grgic of the US Studies Centre in Sydney said the council was "ill-equipped" to deal with the crisis given Russia, France, the US and UK all had veto powers.
"We are not going to see any resolution at that level. But certainly talk of sanctions [against Russia] is very much front and centre," she said.
Has violence flared up in eastern Ukraine?
Heavy shelling has increased in recent days along the tense line of contact between Ukrainian forces and Russian-backed separatist rebels in Donbas.
The conflict there began after Russia's annexed Crimea in 2014.
The fighting has claimed at least 14,000 lives but had been largely quiet for a while.
Ukrainian military spokesman Pavlo Kovalchyuk said Ukrainian positions were shelled 80 times Sunday (local time) and eight times early Monday, noting that the separatists were "cynically firing from residential areas using civilians as shields".
He said Ukrainian forces weren't returning fire.
In the village of Novognativka on the government-controlled side, 60-year-old Ekaterina Evseeva, said the shelling was worse than at the height of fighting.
"It's worse than 2014," she said, her voice trembling.
Russian troops who have been carrying out military exercises in Belarus, which is located on Ukraine's northern border, were supposed to go home when those war games ended Sunday.
But now Moscow and Minsk say that the Russian troops are staying indefinitely.
The continued deployment of the Russian forces in Belarus raised concerns that Russia could send those troops to sweep down on the Ukrainian capital of Kyiv, a city of 3 million less than a three-hour drive away from the Belarus border.
How have Ukrainians responded?
Ukrainians across the country have voiced regret at Mr Putin's decision to recognise independence of parts of Luhansk and Donetsk regions controlled by Russia-backed separatists.
Ukrainian President Volodymyr Zelenskyy accused Mr Putin of wrecking peace talks but said Ukraine was "not afraid of anyone or anything".
He said Ukraine was committed to peace and diplomacy, adding Kyiv expected "clear and effective" steps from its allies to act against Russia.
Mr Zelenskyy called for an emergency summit of the leaders of Ukraine, Russia, Germany and France.
A 20-year-old student from Donetsk, Alexandra Goncharenko, said she was sad when she heard news that her hometown would be independent.
"It's not right that Russia took Donetsk and Luhansk this way," she said.
Olga Tokariuk, a non-resident fellow at the Center for European Policy Analysis, tweeted that Ukrainians had interpreted Mr Putin's speech as a declaration of war.
"If you want to know how Ukrainians react to Putin's speech, here's a glimpse: moms on Facebook discuss putting stickers on their children's clothes, when they go to school, indicating their blood type," she said.
Odessa resident Svetlana Gigashvili said she was saddened by the developments in eastern Ukraine.
"I'd always considered them a part of our country, Ukraine. I visited the region when it was a part of Ukraine," she said.
"It is very sad that the country is being cut up into little bits. It's sad."
Sergei, a resident of Kyiv who did not provide his surname, said the peace Russia "will offer to Donetsk and Luhansk won't be the same as Ukraine could offer".
"They won't have banks working, it would be like in Crimea, but much worse."
Analysts say the current crisis has galvanised a renewed sense of national unity and patriotism in many parts of Ukraine.
Will Biden and Putin meet?
The White House reiterated today that there could be no diplomatic meetings between the US and Russian presidents or foreign ministers if Moscow took further military action in Ukraine.
Mr Biden and Mr Putin had tentatively agreed to meet in a last-ditch diplomatic effort to stave off Moscow's invasion of Ukraine, its first since Russia annexed Crimea from Ukraine in 2014.
Yet both seemed cautious about a possible meeting.
Kremlin spokesman Dmitry Peskov said on Monday (local time) it was "premature to talk about specific plans for a summit".
French President Emmanuel Macron sought to broker the possible meeting between Mr Biden and Mr Putin in a series of phone calls over the weekend.
Mr Macron's office said both leaders had "accepted the principle of such a summit," to be followed by a broader meeting involving other leaders too.
US Secretary of State Antony Blinken and Russian Foreign Minister Sergey Lavrov were to lay the groundwork for the summit at a meeting this coming Thursday, according to Mr Macron's office.
ABC/wires
