MOSCOW, April 20 (Reuters) - A fatal gun battle overnight near the eastern Ukrainian city of Slaviansk shows that the Ukrainian authorities are failing to rein in armed extremists, Russia's foreign ministry said on Sunday.
In a statement, the ministry said an unspecified number of innocent civilians were killed in an attack by armed men from "Right Sector," a far-right nationalist group which figured prominently in the overthrow of Moscow-backed president Viktor Yanukovich in February.
"Russia is indignant about this provocation by gunmen, which testifies to the lack of will on the part of the Kiev authorities to rein in and disarm nationalists and extremists," the statement said.
It said it was a source of surprise that the incident had happened after Russia, the European Union, the United States and Ukraine signed an April 17 accord in Geneva calling on people to desist from using violence or intimidation.
"Russia insists on the strict implementation by Ukraine of the commitments it took upon itself to de-escalate the situation in the south-east of Ukraine," the ministry's statement said. (Reporting by Christian Lowe; Editing by Richard Balmforth)