Russian President Vladimir Putin has officially recognised the independence of Moscow-backed rebel regions in eastern Ukraine and ordered that Russian "peacekeepers" be sent in, fuelling Western fears that an invasion of Ukraine is imminent.
The moves follow days of heightened tensions in Ukraine's eastern industrial heartland, where Ukrainian forces are locked in a nearly eight-year conflict with Russian-backed separatists that has left more than 14,000 people dead.
The United States says Russia may be poised to invade Ukraine with a force of up to 190,000 troops it has amassed near its neighbour's borders.
So, what does Russian recognition of independence mean?
How will the West respond?
Where are the pro-Russian breakaway regions?
In April 2014, Russia-backed rebels seized government buildings in the Donetsk and Luhansk regions — collectively known as Donbas — proclaimed the creation of "people's republics" and battled Ukrainian troops and volunteer battalions.
The following month, the separatist regions held a popular vote to declare independence and make a bid to become part of Russia.
Since then, Ukraine says, about 15,000 people have been killed in fighting.
What is Russia's involvement?
Russia denies being a party to the conflict but has backed the separatists in numerous ways, including through covert military support, financial aid, supplies of COVID-19 vaccines and the issue of at least 800,000 Russian passports to residents.
Moscow has always denied planning to invade Ukraine.
Amid ferocious battles involving tanks, heavy artillery and warplanes, Malaysia Airlines Flight 17 was shot down over eastern Ukraine on July 17, 2014, killing all 298 people aboard.
An international probe concluded that the passenger jet was downed by a Russia-supplied missile from the rebel-controlled territory in Ukraine.
Moscow still denies any involvement.
What does Russian recognition mean for the rebels?
For the first time, Russia is saying it does not regard the Donbas as part of Ukraine.
That could pave the way for Moscow to send military forces into the separatist regions openly, using the argument that it is intervening as an ally to protect them against Ukraine.
A Russian parliament member and former Donetsk political leader, Alexander Borodai, told Reuters last month that the separatists would then look to Russia to help them wrest control of parts of the Donetsk and Luhansk regions still under the control of Ukrainian forces.
If that happened, it could lead to open military conflict between Russia and Ukraine.
Separatist leaders last week released video statements, announcing the evacuation of civilians in the face of what they described as a Ukrainian "aggression".
The data embedded in the video indicated that their statements had been pre-recorded two days earlier when the situation was still relatively calm, suggesting a deliberate plan to try to sever the regions from Ukraine.
Rebel chiefs put out new video statements on Monday, local time, urging Mr Putin to recognise their regions' independence and the Russian leader responded quickly by convening a carefully orchestrated meeting of his Security Council and then signing the recognition decrees in a televised ceremony.
"Ukraine is not just a neighbouring country for us. It is an inalienable part of our own history, culture and spiritual space," Mr Putin said in an address as he announced recognition of the rebel regions.
What about the Minsk Peace Process?
After a massive defeat of Ukrainian troops in August 2014, envoys from Kyiv, the rebels and the Organization for Security and Cooperation in Europe (OSCE) signed a truce in the Belarusian capital of Minsk on September 2014.
The document envisaged a ceasefire, a pullback of all foreign fighters, an exchange of prisoners and hostages, an amnesty for the rebels and a promise that separatist regions could have a degree of self-rule.
The deal quickly collapsed and large-scale fighting resumed, leading to another major defeat for Ukrainian forces at Debaltseve in January-February of 2015.
France and Germany brokered another peace agreement, which was signed in Minsk in February 2015 by representatives of Ukraine, Russia and the rebels.
It envisaged a new ceasefire, a pullback of heavy weapons and a series of moves toward a political settlement.
Ukraine's central government was required to grant special status to the regions, allowing them to create their own police force and have a say in appointing local prosecutors and judges.
A declaration backing the deal was signed by the leaders of Russia, Ukraine, France and Germany.
Russian recognition of the breakaway regions effectively kills off the 2014-15 Minsk peace agreements that, although still un-implemented, have until now been seen by all sides, including Moscow, as the best chance for a solution.
The accords call for a large degree of autonomy for the two regions inside Ukraine.
International players including Chinese officials and French President Emmanuel Macron have emphasised the need to return to the Minsk agreements throughout the current crisis.
How will the West respond?
Western governments have been lining up for months to warn Moscow that any movement of military forces across the Ukrainian border would draw a strong response, including stringent financial sanctions.
US Secretary of State Antony Blinken said last week that recognition "would further undermine Ukraine's sovereignty and territorial integrity, constitute a gross violation of international law, [and] call into further question Russia's stated commitment to continue to engage in diplomacy to achieve a peaceful resolution of this crisis".
He said it would necessitate a "swift and firm" response from the United States and its allies.
Western governments have condemned Mr Putin's announcement as a violation of Ukraine's sovereignty and international law.
Foreign Minister Marise Payne said Australia would work with its allies to ensure "severe costs" for Russian aggression.
Has Russia recognised breakaway regions before?
Yes.
It recognised the independence of Abkhazia and South Ossetia, two Georgian breakaway regions, after fighting a short war with Georgia in 2008.
It has provided them with extensive budget support, extended Russian citizenship to their populations and stationed thousands of troops there.
What are the pros and cons for Moscow?
In the Georgia case, Russia used recognition of the breakaway regions to justify an open-ended military presence in a neighbouring former Soviet republic in an attempt to indefinitely thwart Georgia's NATO aspirations by denying it full control of its own territory.
The same considerations would apply to Ukraine.
On the downside, Moscow faces sanctions and international condemnation for abandoning the Minsk process after long maintaining that it was committed to it.
It will also be saddled indefinitely with responsibility for two territories ravaged by eight years of war and in need of massive economic support.
ABC/wires
