Russia's foreign ministry says a Ukrainian shell exploded in a Russian border town, killing one person and injuring another. It's the first time a fatality was reported in Russian territory.
Ukrainian authorities are denying their forces fired the shell. Russia's Itar-Tass news agency says it came from the Ukrainian side and landed in a border town in the Rostov region.
Russia's foreign ministry summoned a Ukrainian embassy official and said the case represents a qualitative escalation of danger in the border area.
Russia's foreign ministry also warned that such aggression could bring irreversible consequences and that the responsibility lies with the Ukrainian side.
A spokesperson for Ukraine's National Security and Defense Council denied firing a shell into Russian territory and blamed it on Pro-Russian militants.
At the same time, Ukrainian government forces are intensifying their attacks on pro-Russian separatists in the Donetsk and Luhansk regions in eastern Ukraine.
Jul. 13, 2014 - Updated 22:59 UTC