Ukraine's President Volodymyr Zelensky described the situation in Mariupol as "inhuman" and pleaded with the West to deliver heavy weaponry urgently, as Russia claimed control of nearly all of the important port cities and encouraged its last defenders to surrender.

Moscow has ordered Ukrainian forces in the city to lay down their arms by Sunday, following weeks of relative peace in the Ukrainian capital Kyiv being shattered by repeated Russian bombings.

The first European leader to meet with Russian President Vladimir Putin since the invasion began, Austria's chancellor expressed his belief that Putin "believes he is winning the war" in Ukraine.

However, Mariupol has become a symbol of Ukraine's unexpectedly tenacious resistance in the south since Russian forces invaded the former Soviet state on February 24.

Moscow officials now claim complete control of the city, though Ukrainian fighters remain ensconced in the fortress-like steelworks.

"The situation in Mariupol continues to deteriorate. "Inhuman," President Zelensky stated in a video message.

"Russia is purposefully attempting to destroy everyone present."

Mykhailo Fedorov, Ukraine's Minister of Digital Transformation, said that the city was "on the verge of a humanitarian catastrophe" and that the country was accumulating proof of alleged Russian atrocities.

"We will turn over everything to The Hague. "Impunity will not exist," he stated.

Moscow issued an ultimatum to the combatants on Saturday, requesting that they lay down their arms by 6:00 a.m. Moscow time (0300 GMT) and vacate the premises by 1:00 p.m.

However, as Russian forces drew closer, Zelensky delivered his warning.

"The elimination of our troops and men (in Mariupol) will put an end to any negotiations," Zelensky told the Ukrainian news website Ukrainska Pravda.

"Neither our territories nor our people are subject to negotiation."

'Deceptive and ruthless.'

Smoke rose from the capital's Darnyrsky district southeast after Moscow described as "high-precision long-range" strikes on a weapons complex, killing one person and injuring several others.

Sizable police and military presence was established in the facility's vicinity, which had sustained significant damage.

"Our forces are doing everything possible to keep us safe, but our adversary is cunning and ruthless," Kyiv Mayor Vitali Klitschko warned.

The hit came a day after a similar attack on a complex that manufactured Neptune missiles. According to Kyiv and Washington, this type sank Russia's Black Sea flagship Moskva on Thursday.

It was one of the first attacks since Russian soldiers began withdrawing from the region last month, refocusing their efforts on regaining control of the eastern Donbas region, which pro-Russian rebels had primarily controlled for years.

Oleksandr Pavliuk, the regional governor of Kyiv, claimed at least two additional Russian raids on the capital Friday and that people considering returning should "wait for calmer times."

Nonetheless, families and off-duty soldiers were out in downtown Kyiv's parks on Saturday, restoring some sense of normalcy to the once-vibrant city.

"This is the first time we've returned to the city center... It makes me extremely pleased to see people out and about," Nataliya Makrieva, a 43-year-old veterinarian, told AFP.

Meanwhile, in Ukraine's second-largest city, Kharkiv, a Russian missile strike on a residential zone on Saturday killed at least two people in the country's northeast. It injured 18, according to the public prosecutor's office.

Incoming fire in the city's central business district destroyed an industrial kitchen, hurling loaves of bread into the street.

"The blast was so large that we initially had no idea what was happening," volunteer worker Gennadiy Vlasov, 52, told AFP. "When the walls began to move, we all knew we needed to flee."

Furthermore, Ukrainian Interior Minister Denys Monastyrsky stated that three persons were murdered, and four others were gravely injured during a demining operation near the city.

'Political logic'

Austrian Chancellor Karl Nehammer, who met Putin in Moscow on Monday, expressed his belief that the Russian president feels the conflict is essential for his country's security.

"I believe he is now operating under his own war logic," Nehammer said in an interview with NBC's "Meet the Press" that was excerpted Saturday.

"I believe he believes he is victorious."

Russia announced Saturday that it added to the tit-for-tat restrictions imposed since the invasion began by barring British Prime Minister Boris Johnson and several other senior officials from entering the country.

The foreign ministry accused London of "unprecedented hostile actions," particularly sanctions against key Russian officials and "pumping the Kyiv regime with lethal weapons."

Moscow has added Deputy Prime Minister Dominic Raab, Foreign Secretary Liz Truss, and Defence Secretary Ben Wallace to its new entry blocklist.

Johnson had undertaken an unannounced visit to Kyiv a week before and was captured on camera traveling through the capital's deserted streets with Zelensky.

Britain has participated in a global campaign to punish Russia through asset freezes, travel bans, and economic sanctions, while several Western countries have supplied Ukraine with significant weaponry.

Russia warned the US this week that sending its "most sensitive" weapons equipment to Ukraine would have "unpredictable consequences."

Its defense ministry said Saturday that it shot down a Ukrainian transport jet over the Odesa region, transporting weaponry supplied by Western nations.

Meanwhile, Zelensky gave a new warning about the likelihood of Russia utilizing nuclear weapons as the battle progresses, echoing statements made last week by CIA Director William Burns.

Dmitry Peskov, the Kremlin's spokesman, previously told CNN that Russia would use nuclear weapons in the Ukraine conflict only if it faced an "existential threat."

There is no way home.

According to Zelensky, between 2,500 and 3,000 Ukrainian soldiers were killed in the fighting, compared to 19,000 to 20,000 Russians.

Moscow has stated that its losses were significantly less.

Russia's apparent refocus on eastern Donbas, where Russian-backed separatists control the Donetsk and Lugansk regions, would enable Moscow to establish a land corridor to occupy Crimea.

Ukrainian authorities have urged residents of the region to flee immediately in anticipation of a large-scale Russian offensive.

The UN refugee agency issued a warning in Geneva that many of the almost five million people who have left the conflict will be unable to return home.

Many have fled to other countries, with thousands requesting asylum in Israel, according to estimates from the country's immigration ministry.

Numerous Russians have joined them in declaring that they no longer feel secure in their homeland under Vladimir Putin's increasingly harsh regime.

"I was exiled from my country. It was defrauded of me. It was kidnapped by Putin and those KGB goons," Olga Romanova, a Moscow-born linguist, told AFP.