At least seven civilians were reported killed in the Lugansk region where Severodonetsk is located and in the southern city of Mykolaiv, while a revered wooden church was reported to be on fire because of the fighting.

Lugansk regional governor Sergiy Gaiday said in an interview posted online that the invading forces had captured most of Severodonetsk, but that Ukraine's forces were pushing them back.

"The Russian army, as we understand, is throwing all its power, all its reserves in this direction," said Gaiday.

"Our soldiers have managed to redeploy, build a line of defence," said the city's mayor, Oleksandr Striuk, in a televised interview broadcast on Telegram Saturday.

"We are currently doing everything necessary to re-establish total control" of the city, he added. But he acknowledged the situation was "quite difficult", with street fighting and artillery exchanges.

Russia's army claimed some Ukrainian military units were withdrawing from the city.

Severodonetsk is the largest city still in Ukrainian hands in the Lugansk region, where Russian forces have been gradually advancing in recent weeks after retreating or being repelled from other areas, including around the capital Kyiv.

- 'Put Russia in its place' -

Tens of thousands of people have been killed, millions forced to flee and towns turned into rubble since Russian President Vladimir Putin ordered an all-out assault on his pro-Western neighbour on February 24.

Western powers have slapped increasingly stringent sanctions on Russia and supplied arms to Ukraine but divisions have emerged on how to react.

French President Emmanuel Macron said Friday Putin had committed a "fundamental error" but said Russia should not be "humiliated" so that a diplomatic solution could be found.

Ukrainian Foreign Minister Dmytro Kuleba reacted Saturday by saying such calls "only humiliate France" and any country taking a similar position.

"It is Russia that humiliates itself. We all better focus on how to put Russia in its place. This will bring peace and save lives," he said.

Despite diplomatic efforts, the conflict has raged in the south and east of the country.

Ukrainian officials announced Saturday the death of four foreign military volunteers fighting Russian forces but did not specify when or under what circumstances they died.

The International Legion of Defence of Ukraine, an official volunteer brigade, named the men and published photos of them, saying they were from Germany, the Netherlands, Australia and France.

The deaths of the two men named from the Netherlands and Australia had already been reported and France's foreign ministry said Friday a French volunteer fighter had been killed in combat.

Ukraine also reported two victims from a Russian missile strike on Odessa in the southwest, without specifying if they were dead or injured.

Russia's defence ministry said it had struck a "deployment point for foreign mercenaries" in the village of Dachne in the Odessa region.

It also claimed a missile strike in the northeastern Sumy region on an artillery training centre with "foreign instructors".

- Fears over food -

Apart from the human toll, the conflict has caused widespread damage to Ukraine's cultural heritage.

On Saturday, Ukrainian officials reported a large Orthodox wooden church, a popular pilgrim site, was on fire and blamed Russia.

President Volodymyr Zelensky said "Russian artillery again hit" the church, adding bombardment earlier this week had "killed four monks and severely wounded four others".

Russia continues to prove "its inability to be part of the civilised world," Culture Minister Oleksandr Tkachenko said in a statement.

Russia's defence ministry blamed "Ukrainian nationalists" for the blaze and said its forces were not operating in the area.

The church was built in 2009 on the site of another church that was blown up in 1947.

Russian troops now occupy a fifth of Ukraine's territory and Moscow has imposed a blockade on its Black Sea ports, sparking fears of a global food crisis. Ukraine and Russia are among the top wheat exporters in the world.

The United Nations said it was leading intense negotiations with Russia to allow Ukraine's grain harvest to leave the country.

Putin said Friday there was "no problem" to export grain from Ukraine, via Kyiv- or Moscow-controlled ports or even through central Europe.

The UN has warned African countries, which normally import over half of their wheat consumption from Ukraine and Russia, face an "unprecedented" crisis.

Food prices in Africa have already exceeded those in the aftermath of the 2011 Arab Spring uprisings and the 2008 food riots.

After a meeting with Putin in Russia Friday, the head of the African Union, Senegalese President Macky Sall, said he was "very reassured".

Sall added Putin was "committed and aware that the crisis and sanctions create serious problems for weak economies".

Ukraine's Defence Minister Oleksiy Reznikov repeated the government's appeal for the swift delivery of heavy artillery in a telecast address to the Globsec-2022 forum on international security Saturday.

He was asked if Kyiv's forces could push the Russians out of the country by Christmas if they got the equipment they had asked for.

"I cannot forecast definitely what month we will kick them out, but I hope -- and it's absolutely a realistic plan -- to do it this year."

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