Ukraine's "special operation" against pro-Russian separatists in the east of the country has led to heightened concerns of all-out violence in the troubled region.
While Russian President Vladimir Putin criticized the Kiev government for the action, warning that Ukraine was on the verge of a civil war, western leaders have been lining up to condemn Moscow for interfering in the country.
It's a worrying time for Ukraine, which lost Crimea to Russia in February after the region's residents voted overwhelmingly in favor of breaking away.
Here's a look at what could be in store for Ukraine – and what that means for the rest of the world.
Fears of violence
Since the Crimea annexation, tensions have flared once again, with pro-Kremlin rebels occupying a number of government buildings across mainly Russian-speaking eastern Ukraine.
Kiev's attempts to reassert control – which saw it launch a military operation and retake the town of Kramatorsk on Tuesday – may have drawn praise and support from the White House, but they've led to heightened concerns of violence.
"Ukraine could well decide to push ahead with its military action, because of the support it is enjoying at the moment – from the U.S. explicitly," Lilit Gevorgyan, CIS analyst at IHS Global Insight, told CNBC.
"But even if Ukraine manages to supress an uprising in the east, we could still see a rise in social unrest in the coming months. These eastern regions are unmodernized; they don't fit well with Europe but do with Russia."
A key moment in the developing crisis will be the meeting of the European Union (EU), U.S., Ukraine and Russia, due to take place in Geneva on Thursday.
"A lot will depend on the outcome of the discussions," Gevorgyan said, stressing that it was a good sign that - despite the military action by Ukraine - Russia had decided not to boycott the meeting.
"It indicates that Russia is not eager to launch itself into the east and expand its hold in the region," she added.
One possible outcome of the talks could be agreement on how the four powers will oversee Ukraine's constitutional reform and presidential elections on May 25.
Gevorgyan said a peaceful resolution to the situation was crucial for both Ukraine -- which relies on Russia for its energy supplies and orders for its exports -- and Russia, which has invested heavily in Ukraine and has significant business interests there.
The U.S. and EU have already imposed travel bans and asset freezes on a number of Ukrainian and Russian officials, with Moscow retaliating by imposing sanctions of its own. But the West has threatened further sanctions this week if Moscow does not de-escalate the crisis.
"The Ukraine crisis is a wake-up call to the EU. We don't live in some post-modern la-la land, there are external treats… we need a much more vigorous response," Philippe Legrain, author of "European Spring" and former economic advisor to the president of the European Commission, told CNBC.
"We need a much more severe sanctions, asset freezes targeted at Putin and his cronies in the Kremlin… We need to see the bigger picture here: the post-Cold War order is at risk."
But although the West could add to its current restrictions against Russian officials, more severe sanctions look unlikely.
"If there is a Russian intervention and troops cross the Ukrainian border, then we could see trade and energy sanctions, but these are kept for the worst-case scenario," Gevorgyan added.
Concerns about the unfolding dispute between Ukraine and Russia, have also led to fears of a disruptions in gas supply to Europe, given that the Kremlin owns a majority stake in gas giant Gazprom.
Gazprom claims that Ukraine owes it more than $2.2 billion, and has already hinted that it could reduce supply if the debts are not paid. Russia has also hiked gas prices for Ukraine from $268 to $485 per 1,000 cubic meter, scrapping previous discounts, since the start of the unrest.
Russia supplies around a third of Europe's natural gas, and some of that supply is delivered through pipelines running through Ukraine. This heavy reliance on Russia for gas has led to calls for Europe to diversify its supply, with countries like the Netherlands, Norway and Israel mooted as possible alternative suppliers.
But most believe the threat that Russia will cut off gas to its European neighbours – which could result in supply shortages and sharp increases in household energy bills -- is overblown.
"Even at the height of the Cold War, the Soviet Union didn't cut off gas supplies, and Gazprom is entirely reliant on the European market," Legrain said. "It's unlikely they would go down that route."
And even if supply was disrupted, a milder winter this year means that Europe's gas stores are higher than usual.
"The EU could handle disruption to gas supply over the short-term," Gevorgyan said. "For a few weeks at least, but not months."