KVIV, Ukraine — Russia has begun dropping bunker-buster bombs on a Mariupol steel plant where Ukrainians are refusing to surrender, the commander of the Azov Regiment of the National Guard said Monday.

Denys Prokopenko, whose soldiers have been holding out against Russian forces in the key southern port city, said in a video message that the bombs are dropping even though civilians are sheltering in the plant’s tunnels.

“Russian occupational forces, and their proxy … know about the civilians, and they keep willingly firing on the factory,” he said.

Russia estimated that 2,500 Ukrainian troops and about 400 foreign mercenaries were dug in. The U.S. said nearly a dozen Russian battalion tactical groups have been tied up trying to defeat them.

The head of the city’s patrol police, Mikhail Vershinin, told Mariupol television on Sunday that many civilians including children are hiding in the plant, seeking shelter from Russian shelling and forces occupying other parts of the city.

Ukraine estimates that 21,000 people have been killed in Mariupol. Deputy Prime Minister Iryna Vereshchuk warned Russia on social media that refusing to open humanitarian corridors will justify war crimes trials. The Russians, for their part, said “neo-Nazi nationalists” have hampered evacuations.

Zelenskyy Says the Battle for the Donbas Has Begun

Ukrainian President Volodymyr Zelenskyy said Russia has launched its long-feared, full-scale offensive to take control of Ukraine’s east,

“Now we can already state that the Russian troops have begun the battle for the Donbas,” he said in a video address. Zelenskyy said a “significant part of the entire Russian army is now concentrated on this offensive.”

The Donbas is Ukraine’s mostly Russian-speaking industrial heartland in the east, where Moscow-backed separatists have been fighting Ukrainian forces for the past eight years and have declared two independent republics recognized by Russia.

The Kremlin declared the capture of the Donbas its main goal of the war after failing to storm. After withdrawing from the capital, it began regrouping and reinforcing its ground troops in the east for what could be a climactic battle.

“No matter how many Russian troops are driven there, we will fight,” Zelenskyy vowed. “We will defend ourselves. We will do it every day.”

Russian Missiles Kill at Least Seven in Lviv

LVIV, Ukraine — Russian forces launched missile attacks on the western city of Lviv and pounded a multitude of other targets across Ukraine on Monday in what appeared to be an intensified bid to grind down the country’s defenses ahead of an all-out assault on the east.

At least seven people were reported killed in Lviv, where plumes of thick black smoke rose over a city that has seen only sporadic attacks during almost two months of war and has become a haven for large numbers of civilians fleeing intense fighting elsewhere. To the Kremlin’s increasing anger, Lviv has also become a major conduit for NATO-supplied weapons and for foreign fighters joining the Ukrainian cause.

The governor of the Lviv region, Maksym Kozytskyy, said the Russian missile strikes hit three military infrastructure facilities and an auto mechanic shop. He said the wounded included a child, and emergency teams battled fires caused by the attack.

Lviv Is Near Poland Border

Lviv is the biggest city and a major transportation hub in western Ukraine. It sits roughly 50 miles from Poland, a NATO member.

Russia has strongly complained about the increasing flow of Western weapons to Ukraine, and last week its Foreign Ministry issued a formal note of protest to the U.S. and its allies. On Russian state media, some anchors have charged that the supplies amount to direct Western engagement in the fight against Russia.

Lviv has also been seen as a relatively safe place for the elderly, mothers, and children trying to escape the war. But a hotel sheltering Ukrainians who had fled fighting in other parts of the country was among the buildings badly damaged, Mayor Andriy Sadovyi said.

“The nightmare of war has caught up with us even in Lviv,” said Lyudmila Turchak, who fled with two children from the eastern city of Kharkiv. “There is no longer anywhere in Ukraine where we can feel safe.”

A powerful explosion also rocked Vasylkiv, a town south of the capital of Kyiv that is home to a military airbase, according to residents. It was not immediately clear what was hit.

Civilian Evacuations Halted on Monday

Ukraine’s government halted civilian evacuations for a second day on Monday, saying Russian forces were shelling and blocking the humanitarian corridors.

Deputy Prime Minister Iryna Vereshchuk said Ukraine had been negotiating passage from cities and towns in eastern and southeastern Ukraine, including Mariupol and other areas in the Donbas. The government of the Luhansk region in the Donbas said four civilians trying to flee were shot and killed by Russian forces.

Vereshchuk said Russia could be prosecuted for war crimes over its refusal to allow civilians to leave Mariupol.

“Your refusal to open these humanitarian corridors will in the future be a reason to prosecute all involved for war crimes,” she wrote on social media.

The Russians, in turn, accused “neo-Nazi nationalists” in Mariupol of hampering the evacuation.

Russia is bent on capturing the Donbas, where Moscow-backed separatists already control some territory, after its attempt to take the capital failed.

“We are doing everything to ensure the defense” of eastern Ukraine, President Volodymyr Zelenskyy said in his nightly address to the nation on Sunday.

The looming offensive in the east, if successful, would give Russian President Vladimir Putin a badly needed victory to point to amid the war’s mounting casualties and the economic hardship caused by Western sanctions.

Mariupol Reduced to Rubble

The capture of Mariupol is seen as a key step in preparations for any eastern assault since it would free Russian troops up for that new campaign. The fall of the city on the Sea of Azov would also hand Russia its biggest victory of the war, giving it full control of a land corridor to the Crimean Peninsula, which it seized in 2014, and depriving Ukraine of a major port and its prized industrial assets.

Ukrainian Deputy Defense Minister Hanna Malyar has described Mariupol as a “shield defending Ukraine.”

The city has been reduced to rubble in the siege, but a few thousand fighters, by Russia’s estimate, are holding on to the giant, 11-square-kilometer (4-square-mile) Azovstal steel mill.

The relentless bombardment of Mariupol — including at a maternity hospital and a theater where civilians were sheltering — has combined with street fighting to kill at least 21,000 people, by Ukrainian estimates. An estimated 100,000 people remain in the city out of a prewar population of 450,000, trapped without food, water, heat or electricity.

A pro-Russian Ukrainian politician who was arrested last week on a treason charge appeared in a video offering himself in exchange for the evacuation of Mariupol’s trapped defenders and civilians. Ukraine’s state security services posted the video of Viktor Medvedchuk, the former leader of a pro-Russian opposition party with personal ties to Putin.

It was not clear whether Medvedchuk was speaking under duress.

Kharkiv, Ukraine’s second-largest city, was also hit by shelling Monday that killed at least three people, according to Associated Press journalists on the scene. One of the dead was a woman who appeared to be going out to collect water in the rain. She was found lying with a water canister and an umbrella by her side.

Putin Claims Western Sanctions Have Failed

Russia’s President Vladimir Putin says that the barrage of Western sanctions against Russia has failed.

Putin said Monday that the West “expected to quickly upset the financial-economic situation, provoke panic in the markets, the collapse of the banking system and shortages in stores.” He added that “the strategy of the economic blitz has failed.”

The Russian leader spoke in televised remarks during a video call with top economic officials.

Putin did acknowledge a sharp increase in consumer prices in Russia, saying they rose 17.5%.