Moscow, April 20 (IANS): Following the armed clash and killing of three pro-Russian protestors at a checkpoint Saturday, an angry Russia has demanded that Kiev de-escalate tensions in southeast Ukraine.

"On the night of Saturday, the Easter armistice was broken in Sloviansk. The attack of the armed militants from the so-called Right Sector claimed lives of innocent civilians," the Russian foreign ministry said Sunday.

A group of unidentified gunmen attacked a checkpoint controlled by pro-Russia protestors, resulting in the death of three protestors and two gunmen, Xinhua reported.

There was an armed clash between two groups of individuals at a roadblock in Sloviansk in Donetsk region, Ukraine's interior ministry said.

"The Russian side is enraged by the militant provocation which is an indication of the reluctance of the authorities in Kiev to bridle and disarm nationalists and extremists," Russia's foreign ministry said, describing the incident a tragedy.

The ministry said it was surprising that the clash took place after the signing of the Geneva agreement.

Russia insisted on Ukraine's "strict fulfilment" of its commitment and de-escalation of tensions in the southeastern region.

The US, Russia, Ukraine, and the European Union (EU) concluded talks in Geneva Thursday after signing a statement, asking all sides to refrain from violence, intimidation or provocative actions as part of initial steps to restore order in the country.