Russian President Vladimir Putin has held talks with leaders of nations friendly to Moscow amid military setbacks in Ukraine.

Putin is in Kazakhstan's capital Astana to attend a summit of the Commonwealth of Independent States, or CIS, made up of former Soviet republics on Friday.

At the meeting, he said some countries are trying to forget that the Soviet Union saved humanity from Nazi Germany.

He proposed that 2025 be designated as a year of peace and unity in the fight against Nazism. Russia marks the 80th anniversary of the end of World War Two that year.

On Thursday, Putin held separate talks with at least six leaders, including Turkish President Recep Tayyip Erdogan.

Putin is apparently trying to show that Russia is maintaining ties with nations that are friendly to it, and also to reaffirm his grip on the countries he sees as part of Russia's sphere of influence.

He is expected to hold a news conference on Friday after the CIS meetings.

The Institute for the Study of War, a US think tank, said on Thursday that Ukrainian and Russian troops are engaging in fierce battles in the southern region of Kherson, as Ukrainians try to recapture territory.

The institute also said damage to the bridge connecting Russia and Crimea continues to impede the movement of Russian supplies and personnel to southern Ukraine.

It added that the Russian-appointed leader of Kherson, Vladimir Saldo, called for the evacuation of civilians to southern Russia to protect them from missile strikes.

The British defense ministry said in its intelligence report on Friday that pro-Russian forces have made tactical advances towards the town of Bakhmut in the Donetsk region.

But the ministry also said that there have been few, if any, other settlements seized by Russian or separatist forces since early July.

It said forces led by the private Russian military company Wagner Group have achieved some localized gains in the Donbas region, and that Wagner likely remains heavily involved in the fighting in Bakhmut.