Ukraine has reiterated that restoration of its territorial integrity is necessary to resume peace negotiations while stressing that its forces are in a state of active defense.

Ukraine's President Volodymyr Zelenskyy said in a video message on Monday that Ukrainian troops are pushing back Russian forces in some parts of the east and south, mainly in the Donetsk region.

He stated conditions for entering peace negotiations with Russia, including "restoration of territorial integrity," "compensation for all damages caused by the war" and "punishment of every war criminal."

Russia's defense ministry said on Tuesday that defense chief Sergei Shoigu has inspected the command post in Ukraine.

The ministry released a video showing him hearing a report by military commander Sergey Surovikin about the current operational situation. Surovikin also reported on providing reservists called up through partial mobilization "with all types of allowance and supplies."

The video was apparently released to improve the morale of the military amid concerns that many of the reservists die after being sent to the frontlines without sufficient training and equipment. A media report says more than 500 of them -- equivalent to an entire battalion -- were recently killed by Ukrainian shelling in east Ukraine.

The British Defence Ministry said on Tuesday that Russia had started constructing concrete anti-tank structures known as "dragon's teeth" around the occupied southern Ukrainian city of Mariupol.

It added, "This activity suggests Russia is making a significant effort to prepare defenses in depth behind their current front line."