Fighting was reported early June 26 in eastern Ukraine despite a cease-fire between government forces and armed pro-Russian separatists.
ITAR-TASS said gunfire and explosions could be heard at the airport in Kramatorsk and in the nearby city of Slovyansk, in the Donetsk region.
There were few other details.
On June 25, Ukrainian President Petro Poroshenko said there had been "serious violations" by pro-Russian separatists since a unilateral cease-fire by Ukrainian forces began on June 20.
Poroshenko said there had been 52 violations, including the downing of a Ukrainian helicopter on June 24 which killed all nine people onboard.
Western powers warned Russia on June 25 to do more to calm tensions in eastern Ukraine or face fresh, tougher sanctions.
The U.S. State Department said Russia needed to secure its border, stop the flow of fighters and weapons into Ukraine and call on separatists to lay down arms.