The Ukrainian city of Donetsk has been shaken by intense artillery fire following a battle for control over the city's airport.
Three soldiers were killed and 31 others wounded during the battle between government forces and independence-seeking insurgents.
Ukrainian troops annouced that it has retaken the airport.
In the meantime, Ukraine's president Petro Poroshenko has vowed to reassert control over his country's eastern regions.
"In the night our soldiers at Donetsk airport are demonstrating courage, patriotism, heroism and they are an example of how to protect the state. We will not to give an inch of our land."
Poroshenko made the comment while attending a rally in Kiev's central Independence Square, while thousands of people assembled to show solidarity with those killed after a bus was hit by a shell in eastern Ukraine.
Also on Sunday, Russian media reported that Poroshenko has rejected a peace plan proposed by his Russian counterpart, Vladimir Putin.
The plan is said to be proposing a ceasefire between government troops and rebel forces in eastern Ukraine.
