KYIV/KHARKIV, Ukraine (REUTERS) - Russian troops entered the outskirts of the Ukrainian city of Severodonetsk, a regional governor said on Monday (May 30), describing the fighting as “very fierce” in a city that become a key objective for Moscow’s offensive in the Donbas.

Shelling killed two civilians and wounded five others as Russian troops advanced into the city’s southeastern and northeastern areas fringes, Luhansk region Governor Serhiy Gaidai said.

“Unfortunately we have disappointing news, the enemy is moving into the city,” Gaidai told national television.

Incessant shelling has left Ukrainian forces defending ruins in Severodonetsk, but their refusal to withdraw has slowed a massive Russian offensive across the Donbas region in eastern Ukraine.

“Some 90 per cent of buildings are damaged. More than two-thirds of the city’s housing stock has been completely destroyed. There is no telecommunication,” Ukrainian President Volodymyr Zelensky said in a televised speech.

“Capturing Severodonetsk is a fundamental task for the occupiers ... We do all we can to hold this advance.”

Russian Foreign Minister Sergei Lavrov on Sunday said the “liberation” of the Donbas, an industrial region which includes Luhansk and Donetsk, was an “unconditional priority” for Moscow.

Ukrainian forces in the Donbas said they were on the defensive all day on Sunday. Russian forces fired on 46 communities in the Donetsk and Luhansk regions, killing at least three civilians, wounding two others or destroying or damaging 62 civilian buildings.

Russian shelling also continued on Sunday across several regions such as in Novy Buh in Mykolaiv and Sumy.

A Ukrainian soldier on patrol in trenches near the town of Bakhmut, south-west of Severodonetsk, spoke of a nagging fear that his government could be drawn into negotiating an end to the conflict that would result in Ukraine losing territory.

“You know now what I’m most afraid of, now that the fighting is so intense, so tough?” Dmytro, a former English language teacher, told Reuters television. “That we would be told: That’s it, stop it, we have a ceasefire.”

“A negotiated settlement can only happen on Ukrainian terms and at present if it happened it would be a horror,” he said, adding that such a move could end Zelensky’s career.

Having failed to take the capital Kyiv in the early phase of the war, Russia is seeking to consolidate its grip on the Donbas, large parts of which are already controlled by Moscow-backed separatists.

It has concentrated huge firepower on a small area - a contrast to earlier phases of the conflict when its forces were often spread thinly - bludgeoning towns and cities with artillery and air strikes.

The Ukrainian government meanwhile urged the West to provide it with more longer-range weapons in order to turn the tide in the war, now in its fourth month. Zelensky voiced hopes that the weapons would be provided and that he expected "good news" in the coming days.

US officials have said such weapons systems are actively being considered.

Analysts at the Institute for the Study of War in Washington said the Russians had still not managed to encircle Severodonetsk and the Ukrainian defenders have inflicted "fearful casualties" on them.

The Ukrainians were taking serious losses themselves, civilians as well as combatants, they said in a briefing paper.

Russia's focus on Severodonetsk had drawn resources from other battlefronts and as result they had made little progress elsewhere, the analysts said.

A Reuters journalist in the area said a ceramics factory was almost completely destroyed on the outskirts of the Donetsk town of Bakhmut, which straddles the last main road into Severodonetsk and is just 10km from the frontline.

The journalist heard what appeared to be outgoing artillery fire and Russian aircraft dropping a bomb close to the town.

Several transporters with Ukrainian soldiers could be seen in the area.

Embargo on Russian oil

Russia says its special military operation aims to rid Ukraine of nationalists threatening Russian-speakers. Ukraine and Western countries say Russia's claims are a false pretext for a war of aggression and the West has imposed a barrage of sanctions targeting Moscow while delivering shipments of weapons to help the Ukrainian government defend itself.

However, after nearly half a dozen rounds of punitive measures, some against oligarchs close to Russian President Vladimir Putin and banks, the unity within the European Union is being put to fresh test as the bloc on Sunday failed to agree on an embargo of Russian oil. Talks will continue on Monday.

German Economy Minister Robert Habeck expressed fears that EU unity was "starting to crumble". The bloc's leaders are set to meet on Monday and Tuesday in a summit to discuss a new sanctions package against Russia including the oil embargo.

Meanwhile Zelensky - who has won widespread admiration in the West for his leadership in the conflict - visited Ukrainian troops on the frontlines in northeastern Kharkiv region.

Several explosions were heard in Kharkiv city hours after Sunday's visit, a Reuters journalist said, in what was Zelensky's first trip outside the Kyiv region since the invasion began.

A large plume of smoke could be seen rising north-east of the centre of the city, which has been the target of Russian shelling in recent days after several weeks of relative quiet.

"You risk your lives for us all and for our country," the president's office quoted him as telling soldiers as he handed out commendations and gifts.

Elsewhere, Ukraine's military command said its forces were counter-attacking in the southern Kherson region, most of which is occupied by Russia.

Mykolaiv's regional administration said residential areas of Mykolaiv city had been shelled on Sunday morning, killing one civilian and wounding at least six.

Reuters was unable to verify the information.