Ukraine's government has launched a military operation against pro-Russian separatists in the east of the country.
The Ukrainian army sent in troops and issued an ultimatum to the rebels to lay down their arms, after the airport in the city of Donetsk was taken over on Sunday.
Clashes between soldiers and the pro-Russian militia broke out on Monday, with the sounds of automatic weapons and rockets coming from inside the airport compound.
Ukrainian military aircraft were also seen firing at the concrete terminals and runways.
After several hours, government forces finally managed to recapture the complex.
Insurgents said at least 30 rebels were killed and their bodies taken to a hospital a day after the heavy fighting.
However, the mayor of Donetsk said the death toll had since risen to 40 with 31 injured as of Tuesday morning.
Meanwhile, Russia's Foreign Minister Sergei Lavrov has called on Kiev to stop the bloodshed with the immediate halt of military action.
Lavrov added that Moscow was ready for direct talks with Petro Poroshenko, Ukraine's newly elected president.