The Russian military claims it has attacked the headquarters of the Ukrainian army's southern grouping.
The attack was carried out using Russian air force missiles and artillery, Moscow's defence ministry said.
Ukrainian army HQ targeted by missiles, Russia claims
In pictures: Apocalyptic city where Ukrainian troops are desperate for ammunition
Ukrainian forces defending Chasiv Yar have said they are desperately waiting for more ammunition to arrive from the US.
Oleh Shyriaiev, commander of Ukraine's 225th Separate Assault Battalion, which is fighting in the eastern city, called specifically for long-range weapons.
He said they would "cut [Russian forces] off from logistics and supplies".
Commander Shyriaiev also called for cluster munitions, which are banned by a number of countries over the danger they pose to civilians.
Earlier, we reported that Russian troops appear to be concentrating advances in the direction of Chasiv Yar - which is 80km north of Avdiivka.
If captured, the city would give the Russians a better opportunity to target towns and cities further to the west.
The images below show the apocalyptic scenes in Chasiv Yar after bombardment by the Russians.
