Ukrainian President, Volodymyr Zelensky, made a fresh appeal for talks with Moscow on Saturday, while Russia said its soldiers had entered the centre of besieged port city Mariupol.

As bitter fighting between local forces and Russian troops rages across the country more than three weeks into the invasion, the two sides are already holding negotiations remotely.

But so far, as in previous rounds, the talks have yielded little progress, with both sides blaming the other, and none have been at the presidential level.

“This is the time to meet, to talk, time for renewing territorial integrity and fairness for Ukraine,” Zelensky said in a video posted to Facebook.

“Otherwise, Russia’s losses will be such, that several generations will not recover.”

Russia’s offensive remains largely stalled, a US defence official said, with troops about 30 kilometres (20 miles) east of the capital Kyiv and facing heavy resistance.

The official added that Russian forces had made no further progress into the northeastern city of Kharkiv, which they have encircled, and that Ukrainians were also defending the northern city of Chernihiv.

Britain’s defence ministry said Russia was struggling to provide its forward troops “with even basic essentials such as food and fuel” because of Ukrainian attacks on their supply lines.

Russians in Mariupol

But Russia’s defence ministry said Friday that the army and its separatist allies had made a breakthrough in Mariupol, which has been under Russian shelling for days, and were now inside the city.

“In Mariupol, units of the Donetsk People’s Republic, with the support of the Russian armed forces, are squeezing the encirclement and fighting against nationalists in the city centre,” the ministry said.

The mayor of the city confirmed to the BBC that gun battles had reached the heart of Mariupol.

On Friday rescuers were still searching for hundreds of people trapped under the wreckage of a bombed theatre there.

At the time of the attack, Mariupol’s city council said that over 1,000 people were sheltering in the theatre’s basement when it was hit on Wednesday.

On Friday, the council said one person had been badly wounded, but there were no dead, the only casualty tally given so far.

There was still no information about potential fatalities, Zelensky said, but 130 people had been saved so far, some “heavily injured”.

READ ALSO: Russian sanctions grow as Biden set to speak with Xi

9,000 people had been evacuated from Mariupol, he added.

As Putin’s ground offensive has met with fierce Ukrainian resistance, Moscow has increasingly turned to indiscriminate air and long-range strikes.

‘Difficult day’

In the south of Ukraine, the mayor of Mykolaiv Oleksandr Senkevich said on Facebook that several villages in the region had been occupied and the city had been under heavy fire, calling it a “difficult day”.

Ukrainian media reported that Russian forces had carried out a large-scale air strike on Mykolaiv, killing at least 40 Ukrainian soldiers at their brigade headquarters.

Earlier Russian missiles had struck an aircraft repair site close to Lviv’s airport in Ukraine’s far west, extending the war to a relatively unscathed region near the border with NATO member Poland.

According to AFP, Russian defence ministry said the strike was a “high-precision” attack on Ukrainian military infrastructure.

In Kyiv, authorities said one person was killed when a Russian rocket struck residential tower blocks in the northwestern suburbs. They said a school and playground were also hit.

More than 3.25 million refugees have fled Ukraine.

Zelensky accused Russian forces of blocking aid around hotspot areas, saying “they have a strict order to do everything, so the humanitarian catastrophe in Ukrainian cities turned into reason for Ukrainians to work together with the occupiers” — adding “this is a war crime”.

But Russian President Vladimir Putin accused Kyiv of war crimes too in a call with French President Emmanuel Macron, and said Moscow was doing “everything possible” to avoid civilian deaths.

The Star