Ukraine’s interior ministry says the military is now in full control of the airport in the eastern city of Donetsk after a day of bloody clashes.
At least 30 pro-Russia separatists were killed, the insurgents say, after an attempt to take over the airport early on Monday.
New President Petro Poroshenko had vowed to tackle “terrorists” in the east “within hours, not months”.
Meanwhile, the OSCE says it has lost contact with a monitoring team.
The Organization for Security and Co-operation in Europe said four of its monitors were on a routine mission east of Donetsk. Contact was lost at 18:00 (16:00 GMT) on Monday and has not been re-established.
A spokesman told the BBC the monitors were Turkish, Swiss, Estonian and Danish, and all were male.
Seven international military observers linked to the OSCE were taken captive in eastern Ukraine in April and held for a week before being released.
President’s vowUkraine’s Interior Minister Arsen Avakov said in a statement on Tuesday: “The airport is under our full control. The enemy suffered heavy losses. We have none.”
He said operations were still continuing, and a BBC team heard sporadic gunfire.