MOSCOW - A cross-border shell fired from Ukraine was an indication of dangerous escalation of tension in border areas and might have irreversible consequences, the Russian Foreign Ministry said on Sunday.

The response came after local authorities confirmed the death of one Russian citizen after a Ukrainian shell hit Russia's Rostov region earlier Sunday.

Representative of the regional government Aleksandr Titov told ITAR TASS news agency that a shell struck two private houses at about 9:02 a.m. local time (0502 GMT) in the city of Donetsk, which lies near the border with Ukraine's Lugansk region.

One Russian citizen, born in 1967, was killed, he said, while the RIA Novosti news agency quoted a medical source as saying two women were also badly injured.

Investigators from the Russian Investigative Committee said it has opened a criminal case on the shelling.

The Ukrainian charge d'affaires was summoned to the Russian Foreign Ministry where a resolute protest was expressed to him.

Deputy Foreign Minister Grigory Karasin told Rossia-24 channel that the incident "is a qualitative escalation of danger" for Russian citizens on their own territory, and it "will not be left without a reaction."