A local resident walks next to a house destroyed in a Russian shelling in Kramatorsk, Ukraine. AP

After failing to seize Ukraine's capital Kyiv or its second city Kharkiv in its three-month-old war, Russia is trying to take full control of the Donbas, comprised of two eastern provinces Russia claims on behalf of separatists.

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Russia launches new assault on eastern Ukraine towns

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Russia has poured thousands of troops into the region, attacking from three sides in an attempt to encircle Ukrainian forces holding out in the city of Sievierodonetsk and its twin, Lysychansk. Their fall would leave the whole of Luhansk province under Russian control, a main Kremlin war aim.

"The occupiers shelled more than 40 towns in Donetsk and Luhansk region, destroying or damaging 47 civilian sites, including 38 homes and a school. As a result of this shelling five civilians died and 12 were wounded," the Joint Task Force of Ukraine's armed forces said on Facebook.

Ukraine President Volodymyr Zelensky speaks in Kyiv. File photo

It said 10 Russian attacks were repelled, four tanks and four drones destroyed, and 62 "enemy soldiers" killed.

Ukraine President Volodymyr Zelensky's office on Thursday said 11 high-rise buildings were destroyed in Sievierodonetsk and eight in Lysychansk.

Zelensky has said Russian troops heavily outnumber Ukrainian forces in some parts of the east and Kyiv has been trying unsuccessfully to arrange a prisoner swap with Moscow.

Ukrainian prisoners of war held in the Russian-backed self-proclaimed Luhansk and Donetsk People's Republics number about 8,000, Luhansk official Rodion Miroshnik was quoted by TASS news agency as saying.

A man stands next to a destroyed vehicle, as Russia's attack on Ukraine continues, in Vilkhivka, Ukraine. Reuters

"There are a lot of prisoners," Miroshnik said. "Now the total number is somewhere in the region of 8,000. That's a lot, and literally hundreds are being added every day."

Reuters was unable to independently confirm the battlefield reports.

As Russia seeks to solidify its grip on the territory it has seized, President Vladimir Putin signed a decree simplifying the process for residents of newly captured districts to acquire Russian citizenship and passports.

The Russian parliament scrapped the upper age limit for contractual service in the military on Wednesday, highlighting the need to replace lost troops.

In a late night video address, Zelensky, commenting on the new Russian enlistment rules, said: "(They) no longer have enough young men, but they still have the will to fight. It will still take time to crush this will."

Zelensky said this week the conflict could only be ended with direct talks between him and Putin.

Russia calls its actions in Ukraine a "special operation" to disarm Ukraine and protect it from fascists. Ukraine and the West say the fascist allegation is baseless and the war is an unprovoked act of aggression.

A local resident gathers up belongings from his heavily damaged house in Pokrovsk, eastern Ukraine. AP

Ukraine and the West say Russian forces have targeted civilians and have engaged in war crimes, accusations that Russia rejects. A 21-year-old Russian tank commander was jailed for life this week after being found guilty of war crimes for killing an unarmed civilian.

Police in Lysychansk are burying the bodies of civilians in mass graves, Luhansk regional governor Serhiy Gaidai said. Some 150 people have been buried in a grave in one district, he added.

Families of the people buried would be able to carry out a reburial after the war, and police are issuing documents enabling Ukrainians to secure death certificates for loved ones, Gaidai said.

Reuters