Russian Prime Minister Dmitry Medvedev, in an interview to the Russian daily Vedomosti, said that Russia will respond “asymmetrically” if the European Union, or EU, decides to impose further sanctions on the country.

“If there are sanctions related to the energy sector, or further restrictions on Russia's financial sector, we will have to respond asymmetrically,” Medvedev told Vedomosti. “We work on the basis of friendly relations with our partners, and that's why Russia's skies are open to flights. But if we are restricted then we'll have to respond.” 

He also said that a Russian airspace ban “could drive many struggling airlines into bankruptcy.”  

“This is not the way to go. We just hope our partners realize this at some point,” Medvedev reportedly said.

EU leaders had earlier said that they would announce new sanctions on Russia, targeting its defense and oil companies, if the fragile cease-fire in eastern Ukraine fell through. However, European Council president Herman Van Rompuy reportedly said on Sunday that the sanction could be reviewed “if the cease-fire is durable and if the peace talks start.”

Meanwhile, Ukrainian President Petro Poroshenko is expected to visit Mariupol on Monday after shelling was reported in the region over the weekend.

Mariupol, which is a strategic port town on the route to Crimea, the Black Sea peninsula annexed by Russia in March, is the last city in the Donetsk region still under the Ukrainian government's control, BBC reported Monday.

Reuters reported that the cease-fire in eastern Ukraine, marred by a few sporadic violations overnight, seems to be holding Monday. The ceasefire, which took effect on Friday evening, is part of a peace plan intended to end a six-month long conflict triggered in March after Russia annexed Crimea.

More than 3,000 people have been killed in the conflict since April, Zeid Ra'ad Al Hussein, the new United Nations High Commissioner for Human Rights, reportedly said on Monday. On Sunday, Ukrainian security official Volodymyr Poliovyi said that 864 Ukrainian soldiers had been killed since the conflict began, BBC reported.