Ukraine's President Volodymyr Zelenskiy visits a position of Ukrainian service members, as Russia's attack on Ukraine continues, in Lysychansk, Luhansk region, Ukraine June 5, 2022. Picture taken June 5, 2022. Ukrainian Presidential Press Service/Handout
Ukraine's President Volodymyr Zelenskiy visits a position of Ukrainian service members, as Russia's attack on Ukraine continues, in Lysychansk, Luhansk region, Ukraine June 5, 2022. Picture taken June 5, 2022. Ukrainian Presidential Press Service/Handout via REUTERS. Reuters / UKRAINIAN PRESIDENTIAL PRESS SER

Ukrainian forces pulled back to the outskirts of the industrial city of Sievierodonetsk on Wednesday in the face of a fierce Russian assault, the regional governor said, another big swing in momentum in one of the bloodiest battles of the war.

Russia has concentrated its troops and firepower on the small eastern city in recent weeks to secure the surrounding province on behalf of separatist proxies. Ukraine has vowed to fight there for as long as possible, saying the battle could help shape the war's future course.

After announcing a surprise counter-attack last week, the governor of the surrounding Luhansk region said on Wednesday afternoon that most of the city was again in Russian hands.

"...Our (forces) now again control only the outskirts of the city. But the fighting is still going on," Serhiy Gaidai told the RBC-Ukraine media outlet.

Ukrainian forces still controlled all of the smaller twin city Lysychansk on the west bank of the Siverskyi Donets River but Russian forces were causing huge destruction to residential buildings there, he said in an online post.

Russian forces have 10 times more equipment than Ukrainian troops in some areas of Sievierodonetsk, Ukraine's Defence Ministry spokesman Oleksandr Motuzyanyk said. Ukraine has urged its Western allies to speed up delivery of arms, saying the situation would become very difficult for the country if Russia broke through its lines in the east.

"The path to peace lies through heavy weapons," Ukrainian negotiator and presidential advisor Mikhailo Podolyak said on Twitter, reiterating warnings that war could spread to the European Union if Russia was not defeated in Ukraine.

Reuters could not independently verify the situation on the ground in Sieverodonetsk.

Moscow says it is engaged in a "special military operation" to disarm and "denazify" its neighbour. Ukraine and its allies say Moscow has launched an unprovoked war of aggression, killing thousands of civilians and flattening cities. United Nations figures show more than 7 million people have crossed the border from Ukraine since Russia invaded on Feb. 24.

'GOD SAVED ME'

Luhansk and the adjacent province of Donetsk form the Donbas, claimed by Moscow for its proxies who have held eastern parts of the region since 2014. Moscow has been trying to encircle Ukrainian forces in the areas they still hold.

West of Siervierodonetsk in Sloviansk, one of the main Donbas cities in Ukrainian hands, women with small children lined up to collect aid while other residents carried buckets of water across the city.

Most residents have fled but authorities say around 24,000 remain in the city, in the path of an expected assault by Russian forces regrouping to the north.

Albina Petrovna, 85, described the moment her building was caught in an attack, which left her windows shattered and her balcony destroyed.

"Broken glass fell on me but God saved me, I have scratches everywhere...," she said.

Russia has turned its focus to the Donbas since its forces were defeated on the outskirts of Kyiv in March.

Ukrainian President Volodymyr Zelenskiy's office said two people had been killed in the Luhansk region and four killed in the Kharkiv region in the past 24 hours, with others wounded.

In Kharkiv, Ukraine's second-largest city, residents were cleaning up rubble from shelling the previous day. Ukraine pushed Russian forces back last month from the city's outskirts, but Russia still strikes it sporadically.

CCTV footage showed the moment late on Tuesday when a suspected missile struck a shopping mall that included a supermarket, scattering debris and goods. Footage filmed from a drone showed a gaping hole in the roof of the large building.

"The supporting pillars are completely destroyed," said supermarket manager Svitlana Diulina, adding that nobody had been hurt in the attack.

GRAIN SCARE

Ukraine is one of the world's biggest exporters of grain, and Western countries accuse Russia of creating a risk of global famine by blockading Ukraine's Black Sea ports. Moscow says Western sanctions are responsible for food shortages.

Turkey has been trying to broker negotiations to open up the Ukrainian Black Sea ports. Foreign Minister Mevlut Cavusoglu hosted Russian Foreign Minister Sergei Lavrov and said a U.N.-backed deal on the ports was possible with further talks.

Lavrov said the Ukrainian ports could be opened, but Ukraine would have to de-mine them first. Ukraine dismissed Russia's assurances as "empty words" and said Russian attacks on farmland and agricultural sites in the south were exacerbating the crisis.

Vitaliy Kim, governor of the Mykolaiv region, where Russian shelling destroyed the warehouses of one of Ukraine's largest agricultural commodities terminals over the weekend, told Reuters Moscow was trying to scare the world into meeting its terms.

The Kremlin earlier cited Russian President Vladimir Putin as saying Western sanctions must be lifted for Russian grain to reach markets.

Further raising the stakes, the Russian-installed administration in the occupied part of Zaporizhzhia region in southern Ukraine said it planned to stage a referendum later this year on joining Russia. Russian-installed officials in Kherson province further west have announced similar plans.

Some lawmakers from Russia's ruling United Russia party have suggested uniting the Donbas with Russia too. The region has yet to announce a referendum, but the head of the Donetsk province, Denis Pushilin, replaced its government on Wednesday, citing the need to boost "integration processes".

Ukraine and its Western allies regard any planned referendums in occupied areas as illegal and proof that Russia's true aim is territorial conquest.