The Ukrainian military continues to step up its counteroffensive in the country's south, while Russian forces are persistently carrying out assaults on energy infrastructure.

Monday marks eight months since Russia began its invasion of Ukraine. Fighting is likely to intensify as winter approaches.

Ukrainian troops have been advancing in the eastern and southern regions since September to reclaim more territory from Russian control.

Fierce fighting continues in the southern region of Kherson, which was unilaterally annexed by Moscow.

Pro-Russian authorities in the region say evacuations are underway there, and that Russian troops also began retreating.

The region's main city of Kherson has been occupied by Russians since March.

Russian forces have carried out a barrage of missile and drone attacks targeting Ukrainian power plants and other energy facilities in recent weeks.

The attacks have knocked out electricity across Ukraine. Russia is apparently trying to put psychological pressure on Ukrainian people as the weather gets cold.

Independent Russian online media outlet Meduza reported that the private Russian military company Wagner Group began constructing lines of defenses in the eastern region of Luhansk and elsewhere this month.

The defensive lines are created to block Ukrainian tanks. It is also reported that landmines will be placed along the rows of concrete blocks.

Satellite images show the blocks as well as trenches being dug.

Meanwhile, Russia's defense ministry said its minister Sergei Shoigu spoke by phone with his US counterpart Lloyd Austin on Sunday. The two held phone talks two days earlier.

Shoigu also spoke by phone separately with the defense ministers of France, Turkey and Britain on Sunday.

Observers are wondering what Shoigu discussed in these talks, amid growing fears that Russian President Vladimir Putin could resort to the use of nuclear weapons.