Ukraine's military commander-in-chief says troops will be pulled out of the eastern Ukrainian city of Avdiivka, where Russian forces are intensifying their assault.

Oleksandr Syrskyi announced in a social media post on Saturday that the decision was made "to avoid encirclement and preserve the lives and health of servicemen."

Syrskyi said on Wednesday that he visited Avdiivka and other frontline locations. He described the conditions as extremely difficult.

The Russian military has stepped up its offensive against Ukraine's key defensive position since around last October in an effort to take control of the entire Donetsk region in the east.