One Ukrainian serviceman was killed and eleven were wounded in fighting at Donetsk airport as of 15.30 Kyiv time on Friday, Ukrainian presidential advisor Yuriy Biryukov said on Facebook.

Biryukov denied reports that militants have used "toxic gas," saying the smoke had come from burning plastic and smoke grenades.

At the same time, Vladyslav Selezniov, an official with the Ukrainian General Staff, said the fighting continues in Donetsk airport. "The situation is extremely difficult and dynamic, it is changing rapidly," Selezniov told Interfax-Ukraine on Friday.

Selezniov said the headquarters is doing everything possible to support the Ukrainian military who remain in the airport, specifically, with fire support.