(CNN)It's the worst fighting Europe has seen in 20 years.
A serious worsening of the conflict in eastern Ukraine, which started last spring, has thrust the Eastern European nation back in the international spotlight.
How bad has the situation flared up? There has been a "grave escalation" of fighting, and the situation is "dire," in the words of a senior U.S. State Department official.
The United Nations has warned of a growing number of civilian deaths as Ukrainian forces battle pro-Russian separatists for control in the Donetsk and Luhansk regions.
What's the situation today?
Over the past few weeks, fighting has intensified in eastern Ukraine, particularly in the Donetsk region. The United Nations says the number of civilian casualties is climbing. Ukraine's government and the West accuse Russia of backing the separatist forces fighting Ukraine's military with arms, personnel and heavy equipment. Russia denies that.
Why does it matter?
Claims by the West that Russia is backing the separatists have plunged East-West relations to their lowest point since the end of the Cold War. Russia has shown little sign of willingness to change its stance despite the economic damage it's suffering as a result of Western sanctions.
How did we get here?
The unrest began in late 2013, leading up to the Ukrainian Parliament's ouster last February of pro-Moscow President Viktor Yanukovych. Russia annexed Ukraine's Crimean Peninsula a few weeks later, with fighting breaking out in April in two Ukrainian regions bordering Russia -- Donetsk and Luhansk. Separatist leaders there declared independence from Ukraine and sided with Russia. Despite efforts to forge a peace deal in September, there's been an uptick in violence in recent weeks. Many people in eastern Ukraine speak Russian and look to Moscow, not Kiev, for direction.
What does Russia say?
Moscow denies interfering in the conflict in eastern Ukraine. It has acknowledged that there are some Russian soldiers there but says they are volunteers. President Vladimir Putin has accused NATO of trying to expand its presence toward Russia. Moscow also accuses Ukraine of causing civilian casualties through its military campaign against the separatists.
What might happen next?
A new diplomatic push is under way, with French President Francois Hollande and German Chancellor Angela Merkel promoting a joint proposal for new peace negotiations. They are due to meet with Ukrainian President Petro Poroshenko and Putin. Meanwhile, NATO is beefing up its rapid response capacity and is considering establishing new command and control units in its eastern member states, near Russia's western border. This might provoke Russia -- which is concerned about what it sees as NATO expansion toward its border -- to take an even tougher stance.
What happened to the last peace plan?
Representatives of Ukraine, Russia and the separatists in the Donetsk and Luhansk regions signed a peace agreement in Minsk, Belarus, in September. It envisaged a ceasefire and the creation of a buffer zone between the warring sides, as well as constitutional changes. However, it quickly crumbled amid continued fighting.
What other steps has the West taken?
The European Union and United States have imposed a series of financial sanctions against Russian interests and those of separatist leaders in Ukraine. European leaders have said they'll add new names to the list. Russia has also suffered diplomatic isolation.