Embattled Ukraine is pleading with the international community to step up support as Russian forces intensify their assault on the Ukrainian city of Sievierodonetsk.

Slow, solid Russian gains in recent days have seen the capture of Lyman, a nearby rail hub, prompting the call for longer-range weaponry from the West to help defenders fight back in the Donbas region.

Russia’s hard-won gains point to a subtle momentum shift in the war, now in its fourth month.

The invading forces appear close to seizing all of the Luhansk region of Donbas, one of the more modest war goals the Kremlin set after abandoning its assault on Kyiv in the face of Ukrainian resistance.

Russia’s defence ministry said on Saturday its troops and allied separatist forces were now in full control of Lyman, the site of a railway junction west of the Siverskyi Donets River in the Donetsk region that neighbours Luhansk.

Last holdout

However, Ukraine’s deputy defence minister, Hanna Malyar, said the battle for Lyman continues, the ZN.ua website reported.

Sievierodonetsk, some 60 km from Lyman on the eastern side of the river and the largest Donbas city still held by Ukraine, was under heavy assault by the Russians.

“Sievierodonetsk is under constant enemy fire,” Ukrainian police posted on social media on Saturday.

Russian artillery was also shelling the Lysychansk-Bakhmut road, which Russia must take to close a pincer movement and encircle Ukrainian forces.

The governor of Luhansk, which along with Donetsk comprises the Donbas, said on Friday Russian troops had already entered Sievierodonetsk.

Ukrainian troops may have to retreat from the city to avoid capture, Governor Serhiy Gaidai said. It was not clear whether they had begun to pull out on Saturday.

Ukrainian presidential adviser and peace talks negotiator Mykhailo Podolyak on Saturday repeated a call for deliveries of US-made long-range multiple-rocket launchers.

U.S. officials tell Reuters such systems are actively being considered, with a decision possible in the coming days.

‘We need effective weapons’

“It is hard to fight when you are attacked from 70 km away and have nothing to fight back with. Ukraine can return Russia behind the Iron Curtain, but we need effective weapons for that,” Podolyak tweeted.

President Volodymyr Zelenskiy voiced hopes in a late-night video address that allies would provide needed weaponry and added that he expected “good news on this next week.”

The Ukrainian military said on Saturday its troops had repelled eight assaults in Donetsk and Luhansk in the previous 24 hours.

The British defence ministry said in its daily intelligence report that if Russia succeeded in taking over those areas, the Kremlin would likely view it as a “substantive political achievement,” one it could use to justify its invasion to the Russian people.

Zelenskiy said the military situation in the Donbas region was very complicated, adding that defences were holding up in a number of places, including Sievierodonetsk and Lysychansk.

“It’s indescribably difficult there. And I am grateful to all those who withstood this onslaught,” he said in his late-night video address.

In a television interview, Zelenskiy said he believed Russia would agree to talks if Ukraine can recapture all the territory it has lost since the invasion began on February 24.

Still, Zelenskiy ruled out the idea of using force to win back all the land Ukraine has lost to Russia since 2014, which also includes Crimea, annexed that year by Moscow.

“I do not believe that we can restore all of our territory by military means. If we decide to go that way, we will lose hundreds of thousands of people,” he said.

Russia says it is waging a “special military operation” to demilitarise Ukraine and rid it of nationalists threatening Russian-speakers there. Kyiv and Western countries say Russia’s claims are a false pretext for war.

Thousands of people, including many civilians, have been killed and several million have fled their homes, either for safer parts of Ukraine or to other countries.

– with AAP