Russian forces are trying to press their offensive deeper into eastern Ukraine after taking control of a key stronghold.

The Ukrainian military confirmed its forces had withdrawn from the city of Lysychansk, the last bulwark of Ukrainian resistance in the Luhansk province, one of the two regions that make up the country’s eastern industrial heartland of Donbas.

The Russians also control about half of Donetsk, the second province of Donbas.

Luhansk governor Serhii Haidai said Ukrainian forces retreated from Lysychansk to avoid being surrounded.

POLITICS Ukraine(PA Graphics)

“There was a risk of Lysychansk encirclement,” Mr Haidai told the Associated Press, adding that Ukrainian troops could have held on for a few more weeks but would have potentially paid too high a price.

“We managed to do a centralised withdrawal and evacuate all injured,” Mr Haidai said. “We took back all the equipment, so from this point withdrawal was organised well.”

The General Staff of the Ukrainian military said Russian forces are focusing their efforts on pushing towards the line of Siversk, Fedorivka and Bakhmut in the Donetsk region.

The Russian army has also intensified the shelling of key Ukrainian strongholds of Sloviansk and Kramatorsk deeper in the Donetsk region.

On Sunday, six people, including a nine-year-old girl, were killed in the Russian shelling of Sloviansk and another 19 people were wounded, according to local authorities.

Kramatorsk also came under fire on Sunday.

An intelligence briefing on Monday from the British MoD supported the Ukrainian military’s assessment, noting that Russian forces will “now almost certainly” switch to capturing Donetsk.

The briefing said the conflict in Donbas has been “grinding and attritional”, and is unlikely to change in the coming weeks.

While the Russian army has a massive advantage in firepower, military analysts say that it does not have any significant superiority in the number of troops.

That means Moscow lacks resources for quick land gains and can only advance slowly, relying on heavy artillery and rocket barrages to soften Ukrainian defences.

Russian President Vladimir Putin has made capturing the entire Donbas a key goal in his war in Ukraine, now in its fifth month.

Moscow-backed separatists in Donbas have battled Ukrainian forces since 2014 when they declared independence from Kyiv after the Russian annexation of Ukraine’s Crimea.

Ukrainian President Volodymyr ZelenskyUkrainian President Volodymyr Zelensky (Nariman El-Mofty/AP)

Russia formally recognised the self-proclaimed republics days before its February 24 invasion of Ukraine.

Mr Putin’s defence minister reported to him on Sunday that the Russian army and its separatist allies now hold all of the Luhansk region after taking “full control” of Lysychansk.

In his nightly video address, Ukrainian President Volodymyr Zelensky acknowledged the withdrawal, but vowed that Ukrainian forces will fight their way back.

“If the command of our army withdraws people from certain points of the front where the enemy has the greatest fire superiority, in particular this applies to Lysychansk, it means only one thing: we will return thanks to our tactics, thanks to the increase in the supply of modern weapons,” Mr Zelensky said.

Since failing to take Kyiv and other areas in Ukraine’s north-east early in the war, Russia has focused on Donbas, unleashing fierce shelling and engaging in house-to-house combat that devastated cities in the region.

Russia’s invasion has also devastated Ukraine’s agricultural sector, disrupting supply chains of seed and fertiliser needed by Ukrainian farmers and blocking the export of grain, a key source of revenue for the country.

Russian soldiers set a Russian national flag and a replica of the Victory banner atop of the administration after capturing the eastern village of BilohorivkaRussian soldiers with a Russian national flag and a replica of the Victory banner in the eastern village of Bilohorivka (Russian Defence Ministry Press Service/AP)

In its Monday intelligence report, the MoD pointed to the Russian blockade of the key Ukrainian port of Odesa, which has severely restricted grain exports.

It predicted that Ukraine’s agricultural exports would reach only 35% of the 2021 total this year as a result.

As Moscow pushed its offensive across Ukraine’s east, areas in western Russia came under attack on Sunday in a revival of sporadic apparent Ukrainian strikes across the border.

The governor of the Belgorod region in western Russia said fragments of an intercepted Ukrainian missile killed four people on Sunday.

In the Russian city of Kursk, two Ukrainian drones were shot down, according to the Russian Defence Ministry.