Defense officials in Ukraine say there has been no letup in efforts by pro-Russia separatist fighters in the east to capture the airport in the main rebel-held city of Donetsk.

Security spokesman Andriy Lysenko said Tuesday that rebels fired on the terminal from tanks, artillery systems and multiple rocket launchers.

A cease-fire that nominally came into effect one month ago has been routinely flouted, with substantial shelling concentrated in the area around Donetsk airport. Fighting has also been reported in numerous other parts of the Donetsk region.

Residential buildings are frequently hit as a result of the shelling duels. Donetsk city authorities say four civilians were killed Monday.

Rebels and government officials regularly trade accusations over who is responsible for the civilian deaths.