KIEV — Ukraine's President Volodymyr Zelenskyy on Monday said "tens of thousands of civilians" must have been killed in Mariupol. He believed the Russian military had killed "tens of thousands" of people in the besieged city of Mariupol and asked South Korea for military assistance.

The war is now in its seventh week, with Russian forces now concentrating their offensive on eastern Ukraine, after retreating from the capital Kiev.

Addressing South Korea's National Assembly via video conference, Zelenskyy said Russia had "completely destroyed" the port in southeastern Ukraine.

"It was a city of half a million people. The occupiers besieged it and did not even allow water and food to be brought there. The Russians completely destroyed Mariupol and reduced it to ashes. At least tens of thousands of citizens of Mariupol must have been killed," he said.

The Ukrainian president accused Russia of wanting to make Mariupol "an example", calling on South Korea to help his country fight the Russian invasion by providing it with military equipment, "from planes to tanks".

Austrian Chancellor Karl Nehammer will visit Moscow on Monday for talks with Russian President Vladimir Putin, the first EU leader to visit since the start of the war amid news that Russia has appointed a new Ukraine war commander, Gen. Alexander Dvornikov, a veteran of the Russian campaign in Syria.

Austria’s foreign minister said Chancellor Karl Nehammer is taking “very clear messages of a humanitarian and political kind” to a meeting with Putin in Moscow.

Foreign Minister Alexander Schallenberg said Monday that Nehammer decided to make the trip after meeting in Kiev on Saturday with Ukrainian President Zelenskyy and following contacts with the leaders of Turkey, Germany and the European Union.

Schallenberg said ahead of a meeting with his EU counterparts in Luxembourg that “We don’t want to leave any opportunity unused and must seize every chance to end the humanitarian hell in Ukraine.”

He added, “Every voice that makes clear to President Putin what reality looks like outside the walls of Kremlin is not a wasted voice.”

Schallenberg said that Nehammer and Putin would meet one-on-one without media opportunities. He insisted that Austria has done everything to ensure that the visit isn’t abused, “and I think he (Putin) himself should have an interest in someone telling him the truth and really finding out what’s going on outside."

Britain's Ministry of Defense said Russia needs to boost troop numbers with extra recruitment, due to mounting losses in the war, while, European Union foreign ministers meeting to weigh the effectiveness of the bloc’s response to Russia's invasion.

The Croatian Foreign Ministry said that 24 staff at the Russian embassy in Zagreb would be expelled from the country. The staff include 18 diplomats and 6 members of the administrative and technical staff of the Russian embassy.

Croatia's Foreign Ministry said they had expressed "the strongest condemnation of the brutal aggression against Ukraine and numerous crimes committed" to the Russian ambassador who was summoned to the ministry.

Many EU countries have expelled Russian diplomats since the war in Ukraine began in late February, stating that they posed a threat to the countries' national security.

In another development, Slovakia has denied its S-300 air defense missile system it transported to Ukraine has been destroyed by the Russian armed forces.

“Our S-300 system has not been destroyed,” Lubica Janikova, spokeswoman for Slovakia’s Prime Minister Eduard Heger said in a statement sent to The Associated Press. She said any other claim is not true.

Earlier on Monday, the Russian military said it destroyed a shipment of air defense missile system provided by the West on the southern outskirts of the city of Dnipro.

The Russian side said Ukraine had received the air defense system from a European country that he didn’t name. Last week, Slovakia said it has handed over its Soviet-designed S-300 air defense systems to Ukraine, which has pleaded with the West to give it more weapons, including long-range air defense systems.

The Ukrainian army said on Monday that they expect a Russian offensive "very soon" in the east. Many officials think eastern Ukraine has become the Kremlin's main target, after Russian troops retreated in the northern region of the country and around Kyiv.

“According to our information, the enemy has almost completed its preparation for an assault on the east. The attack will take place very soon,” said Defense Ministry spokesman Oleksandr Motuzyanyk.

Meanwhile, Ireland’s foreign minister says the European Union should consider imposing sanctions on Russia’s oil industry but cautions that it’s most important for the 27-nation bloc to remain unified.

Several EU countries are dependent on Russian oil and gas imports. After much debate, the bloc agreed last week to a phase-in of restrictions on imports of coal over Moscow’s war on Ukraine.

Irish Foreign Minister Simon Coveney said, “We need to take a maximalist approach to sanctions to offer the strongest possible deterrents to the continuation of this war and brutality.”

Speaking as EU foreign ministers gathered Monday in Luxembourg, Coveney said “that should include, in our view, oil. We know that that’s very difficult for some member states and we have to keep a united position across the EU.”

The EU’s executive arm, the European Commission, is assessing what more can be done with a fresh package of sanctions. Coveney said “the European Union is spending hundreds of millions of euros on importing oil from Russia. That is certainly contributing to financing this war. And in our view, we need to cut off that financing of war.”

The World Bank reported that the Ukraine's economy will shrink by 45.1% this year because of Russia's invasion, which has shut down half of the country's businesses, choked off imports and exports, and damaged a vast amount of critical infrastructure.

Unprecedented sanctions imposed by Western allies in response to the war, meanwhile, are plunging Russia into a deep recession, lopping off more than a tenth of its economic growth, the World Bank said in a report.

The war is set to inflict twice the amount of economic damage across Europe and Central Asia that the COVID-19 pandemic did, the Washington-based lender said in its “War in the Region” economic report.

“The magnitude of the humanitarian crisis unleashed by the war is staggering," said Anna Bjerde, the World Bank's vice president for the Europe and Central Asia region. "The Russian invasion is delivering a massive blow to Ukraine’s economy and it has inflicted enormous damage to infrastructure.”

The report said economic activity is impossible in "large swaths of areas" in Ukraine because productive infrastructure like roads, bridges, ports and train tracks have been destroyed.

The World Bank said the humanitarian catastrophe would be the biggest shockwave from the war and likely its most enduring legacy, as the wave of refugees fleeing Ukraine is "anticipated to dwarf previous crises."

More than 4 million people have fled Ukraine, with more than half going to Poland and others heading to countries like Moldova, Romania and Hungary. An additional 6.5 million have been displaced internally. Those numbers are expected to swell as the war drags on, the World Bank said. — Euronews