At least 30 pro-Russian separatists were killed by Ukrainian troops Monday as the government continued its push to reclaim an occupied city, the country's interior minister said.
At least four Ukrainian troops were also killed and another 20 injured in gunbattles on the outskirts of Slovyansk, Arsen Avakov said in a Facebook post Tuesday.
The Defense Ministry said Monday a helicopter was shot down but both pilots survived, and that its forces have now effectively surrounded the city in an attempt to squeeze the occupying militias.
The area is one of several towns and cities in the Donetsk and wider region that were last month seized by armed groups demanding closer ties with Russia.
Separatist leader Igor Strelkov had earlier told the Kiev Post that around 10 of his men were killed and as many as 25 wounded in the fighting.
Meanwhile, the region's largest largest airport announced Tuesday that all flights had been temporarily suspended "by order of the State Aviation Authority of Ukraine." It did not give a reason for closure and its online departure board showed flights from Donetsk to the capital Kiev still going ahead.