Fighting in the Donetsk region, with drastic consequences, has shattered the latest hopes of securing a ceasefire in eastern Ukraine.
In a symbolic blow to government forces, the army has lost control of Donetsk airport to the rebels.
The military said its forces had withdrawn from the main terminal.
Pictures from Russian television showed pro-Russian rebels from the self-proclaimed “Donetsk People’s Republic” handling ammunition and weapons left behind by government troops.
Only three years ago the shiny new complex was the pride of Ukraine – built for the 2012 Euro football tournament for an estimated 800 million euros.
But since last spring rockets and shells have replaced airliners, the runway and terminal buildings reduced to rubble in the relentless battles between army and separatists.
The city itself has been traumatised by the reported deaths of more than a dozen civilians, hit by shelling at a bus stop.
Images showed the wreckage of a bus hit by a shell or a mortar bomb, its destinations still flashing on a cracked screen.
Passengers were among at least 13 civilians said to have died. One witness saw seven bodies on the ground nearby.
The scene has been visited by international observers from the OSCE.
The explosion blew out nearby windows and caused extensive damage.
But once again who was responsible is bitterly contested.
According to reports, dozens of civilians and soldiers have been killed within a 24-hour period in the Donetsk and Luhansk regions.
Shelling destroyed dozens of houses in the town of Makiivka near Donetsk.
One local resident blamed Ukrainian forces.
As each side fears the other is planning a new offensive, the upsurge in fighting has heightened fears for civilians and wrecked diplomatic moves.
On Wednesday evening, the Ukrainian and Russian foreign ministers had joined their French and German counterparts in calling for a ceasefire after talks in Berlin.