Russian forces are believed to be focusing their assaults on major targets in the Donetsk region with the aim of taking full control of the eastern Ukrainian region.

Russia's defense ministry said on Wednesday that its missile attacks destroyed two HIMARS rocket systems given to Ukraine by the United States near Kramatorsk, Ukraine's stronghold in the Donetsk region.

The Ukrainian side denied the Russian announcement, saying it is "nothing but a fake."

Britain's defense ministry said in a Twitter post on Thursday, "Heavy shelling continued along the Donetsk front line, but with few advances being made by Russia. Russian units involved in last week's gains are now likely re-constituting."

Analysts at the Institute for the Study of War in Washington said on Wednesday that Russian forces "attempt to set conditions for more significant offensive operations and rebuild the combat power needed to attempt those more ambitious undertakings."

On Monday, Russian President Vladimir Putin told Defence Minister Sergei Shoigu that the military units that took part in an operation in the Luhansk region, which Russia declared it had captured, "should rest and build up their combat capabilities."

Ukrainian President Volodymyr Zelenskyy said in a video address on Wednesday, "The weapons we received from our partners started working very powerfully. The losses of the occupiers will only increase every week, as will the difficulty of supplying them."