Ukraine said on Saturday that Russia had thrown all its available forces into the battle for Severodonetsk (east), a key city in the Donbass region where Moscow is concentrating its offensive in the hope of taking full control.

“The situation in the whole region is extremely difficult. The fighting is currently concentrated in Severodonetsk, because, from what we have been able to understand, the Russian army has thrown all its weight and its reserves” into this battle, said the governor of the Lugansk region, Sergei Gaïdaï, in an interview on his official social networks.

“Initial information indicates that they have succeeded in taking control of most of the city. But our forces are repelling them now,” he said.

It is in this region of Donbass that a long-term "war of attrition" is now being played out, warned NATO Secretary General Jens Stoltenberg.

Taking the city of Severodonetsk would allow Russia to secure its hold on the Donbass, a mining basin partially occupied by pro-Russian separatists since 2014.