Ukraine said Sunday it had nothing to do with the shelling of a Russian town earlier in the day, which left one dead and two more injured.
"Ukrainian servicemen did not, do not and will not deliver fire against the neighbouring country's territory or residential areas," Xinhua quoted Ukrainian foreign ministry as saying in a statement.
It also urged Moscow to be "objective and unbiased" when assessing the causes of the incident in the city of Donetsk in Russia's Rostov region, which lies near the border with Ukraine's Lugansk region.
Kiev's statement came hours after Russian foreign ministry said the cross-border shelling was an indication of dangerous escalation of tension in border areas and might bear irreversible consequences.
Russian 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".
Also on Sunday, Ukraine's National Security and Defence Council said seven servicemen were killed and 30 others were injured in the past day during clashes in eastern regions.
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Andrey Lysenko, spokesperson of the Council, said separatists have shelled several residential areas of Ukraine's Donetsk region, which killed six civilians and wounded eight others.
Increasing casualties have been reported since Ukraine's government troops resumed military action in southeastern regions since the start of the month. Moscow has repeatedly warned of a humanitarian catastrophe in Ukraine, claiming more than 20,000 Ukrainian citizens had officially applied for refugee status in Russia.