Ukrainian forces are battling pro-Russian rebels at the international airport of the eastern city of Luhansk, a Ukrainian military official has said, reports GHN based on BBC.
The separatists earlier claimed they had seized the airport, but the army said the fighting was still ongoing.
Russian Foreign Minister Sergei Lavrov has urged negotiators meeting later in Belarus to make an "immediate ceasefire" their priority.
Some 2,600 people have died in eastern Ukraine since fighting began in April.
The conflict broke out after Russia's annexation of Ukraine's southern Crimea peninsula in March.
The rebels have been gaining ground on Ukrainian forces in recent days, in both the Luhansk and Donetsk regions, and further south around the port of Mariupol.

Ukraine and the West blame Russian military support for the rebel advances, saying armoured columns have crossed the border - allegations rejected by Russia's President Vladimir Putin.
He has accused European leaders of ignoring the Ukrainian army "directly targeting civilians".
On Sunday, he said the issue of "statehood" for eastern Ukraine needed to be discussed to ensure the interests of local people were "definitely upheld".