Russia 'Outraged' by Deadly Ukraine Shootout

Kiev calls incident a "cynical provocation" by the pro-Russian side.

DONESTK, Ukraine, April 20, 2014— -- The Russian government said today it is "outraged" by a shootout overnight near Slovyansk that left at least three dead, saying the attack was carried out by a Ukrainian right-wing nationalist group.

The attack took place before just before 2:30 a.m. on the outskirts of Slovyansk, a town under the control of pro-Russian forces. Four vehicles reportedly approached a checkpoint and opened fire, and video of the aftermath showed spent bullet casings and two burned out vehicles.

According to Ukraine's Interior Ministry, three people were killed and three wounded in clashes between armed groups, but it denied Ukrainian forces played any role. The Sloviansk hospital declined ABC News' request for comment, but Slovyansk's pro-Russia mayor confirmed the three dead to reporters.

Read More: Ukraine Suspends 'Anti-Terrorist' Operation in East

"The Russian side is outraged with the provocation, which indicates that Kiev is unwilling to put in check and disarm nationalists and extremists," Russia's Foreign Ministry said in a statement posted by the state-run Russia Today channel.

Moscow "insists on the strict implementation by the Ukrainian side of its commitments to de-escalate the situation in southeastern Ukraine," the ministry statement said.

Ukraine's Security Service called the incident a "cynical provocation" by "armed offenders and saboteurs who are terrorizing the local population in Slovyansk."

PHOTOS: Crisis in Ukraine

A pro-Kremlin website posted video of what it said was evidence of the nationalist group Right Sector's involvement in the attack, including crisp $100 bills, Google Maps satellite images of the area, bullets and the business card of the group's leader.

Sloviansk's new mayor quickly calling on Russian President Vladimir Putin to send Russian "peacekeepers" to defend the region's citizens from "fascists and imperialists."

On Thursday, foreign ministers from the United States, Russia, Ukraine and the European Union signed an agreement that "all illegal armed groups must be disarmed" and that "all illegally seized buildings" in Ukraine must be vacated. But the armed groups occupying those buildings in eastern Ukraine haven't moved, arguing that the "criminal" government in Kiev has to first step down.