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The Ukraine conflict is moving fast. Here's what to watch for

Moscow and Kyiv(CNN) Tensions in Ukraine are escalating. The country's eastern Donbas region -- where fighting between pro-Russian separatists and Ukrainian forces have simmered since 2015 -- experienced its worst shelling in years this week.

And diplomatic efforts to defuse tensions have, so far, failed to reach a conclusion.

As tensions continue to spike, here's some key moments to watch in the ongoing Ukraine crisis.

Ongoing wargames and nuclear drills

Over the past week, Russian President Vladimir Putin has focused international attention onto a series of military drills that have tested Russia's conventional military power. Russia's Ministry of Defense has released flashy footage of live-fire exercises in neighboring Belarus involving tanks, artillery and fighter aircraft, and the wargames have showcased Russia's air defenses and its navy.

On Saturday, Russia is set to test its strategic deterrent: its nuclear forces. The Kremlin announced Friday that Putin is "likely to be in the situation center" during military drills on Saturday, where ballistic and cruise missiles will be launched. Three decades after the end of the Cold War, both Russia and the United States have nuclear arsenals on "hair trigger" alert -- that is, nuclear warheads married up to their delivery systems and ready for launch at a moment's notice.

Kremlin spokesperson Dmitry Peskov noted that such training exercises are "quite regular," and would involve appropriate international notifications. That's true, up to a point: These readiness exercises are happening against the background of international tensions over Ukraine that could actualize into a major war.

Tensions escalate in Donbas

Tensions in Ukraine reached their highest in years on Friday after pro-Russian separatist leaders in the breakaway republics of Ukraine's Donbas region called on civilians to evacuate -- and after an explosion wrecked a vehicle in the separatist-controlled city of Donetsk, creating more war jitters.

A kindergarten in Stanytsia Luhanska, in Ukraine's eastern Donbas region, was hit by a shell on Thursday.

Ukrainian officials deny any plans to retake Donbas by force, saying that they see this week's incidents as an effort by Russia to create a pretext to launch an invasion. But Russian state media have already sounded the alarm, showing images of civilians departing Donbas on buses heading to Russia's Rostov oblast, just across the border.

It is unclear how many civilians will be evacuated or if there will other incidents in Ukraine's east that Russia might seize on as a potential pretext for war.

A diplomatic balancing act

Ukrainian President Volodymyr Zelensky, speaking this week about his country's ambitions to join NATO.

Ukrainian President Volodymyr Zelensky is scheduled to attend the Munich Security Conference on Saturday, despite US President Joe Biden's administration plea to reconsider those plans to leave Ukraine amid concerns about a possible Russian invasion. It's possible that unexpected surprises could cut his visit short.

The US and NATO make moves

The US has already bolstered its military presence in eastern Europe; the US military announced a training mission in Hungary. How will the US and its allies react to the latest moves by Russia? Will we see more evacuations of diplomats remaining in Kyiv?

Olympics end

Russia has said its military drills are slated to end on Sunday, coinciding with the end of the Beijing Winter Olympics. Will the Olympics be remembered as a unifying international moment, or as a tragic preamble to war? That is anyone's guess.

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