Quick Take:

Russian forces made more gains Thursday despite fierce Ukrainian resistance. The civilian death toll, while still unclear, is expected to grow exponentially.

Hundreds were feared dead in the embattled Ukrainian port city of Mariupol on Thursday after more than a day of Russian bombardment left buildings in ruins and civilians cowering in terror.

Russian forces unleashed a barrage of artillery fire, rockets and air attacks Wednesday on the strategic city of some 430,000 people in southeastern Ukraine, on the Sea of Azov near the Russian border, news reports said.

“We cannot count the number of victims there, but we believe at least hundreds of people are dead,” the city’s deputy mayor, Serhiy Orlov, told the BBC. “We cannot go in to retrieve the bodies. My father lives there. I cannot reach him. I don’t know if he is alive or dead.”

Orlov said the situation was approaching a “humanitarian catastrophe,” with food growing scarce. Civilians had also lost access to water, power and sanitation because of strikes on the city’s infrastructure.

Russian troops are said to have surrounded Mariupol on all sides and could capture the port as soon as Thursday, a day after Russian forces apparently seized control of Kherson, a southern port city on the Dnieper River.

“Our internal forces are very brave, but we are surrounded by the Russian army,” Orlov later told CNN.

The capture of Mariupol would bridge the gap between territories held by Russian-backed separatists in eastern Ukraine and Russian soldiers in the southern peninsula of Crimea, which Moscow annexed by force in 2014. It would boost Russia’s chances of extending control across the rest of southern Ukraine and cutting off the country’s access to key shipping routes in the Black Sea.

The desperate conditions in Mariupol paint a grim picture for Ukraine of an overwhelmingly powerful military foe willing to launch more attacks on civilian targets, including schools and hospitals. A prosecutor for the International Criminal Court said late Wednesday that senior Russian leaders were being investigated for war crimes, crimes against humanity or genocide.

Cities such as Kharkiv, Chernihiv and the capital, Kyiv, have come under devastating fire as the Russian military attempts to regain the initiative after its initial assault failed to achieve a rapid victory.

Kyiv was hit by two massive explosions that lit up the city’s sky Wednesday evening and before dawn Thursday. It was not immediately known where the blasts struck.

But a 40-mile-long column of Russian armored vehicles on Kyiv’s northern outskirts “is still stuck there,” British Defense Secretary Ben Wallace said, amid intelligence that the convoy was experiencing fuel and supply shortages.

Nonetheless, fierce fighting across Ukraine is taking a mounting toll on human life, though it remains unclear to what extent. The United Nations’ human rights office said 227 civilians have been confirmed killed and another 525 injured since Russia’s invasion began a week ago. The office warned that the actual death toll was almost certainly vastly higher.

Ukraine’s State Emergency Service has said more than 2,000 civilians have been killed in the invasion.

“One week ago, at 4 a.m., Russia invaded our independent Ukraine, our land,” Ukrainian President Volodymyr Zelensky said Thursday in the latest video address aimed at buoying his people and showing them he remains in place and in charge. “The first hours and days of full-scale were extremely difficult, but we were united and therefore strong, and therefore we withstood. And it will be so, and we will continue to stand.”

Russia’s defense ministry said Wednesday that 498 Russian soldiers had been killed and 1,597 wounded. Ukraine claims about 9,000 Russian troops have died.

“What we’ve seen in Ukraine is beyond … anybody’s idea of what might happen,” Wallace said at a news conference in Estonia. “Not only has Russia illegally invaded Ukraine, it is now unleashing violence on civilian areas, bombardments, and inflicting casualties on potentially thousands of civilians.”

He said it was still too early to tell if Russian forces had succeeded in fully capturing Kherson, a city of some 300,000 that would grant Russia access to a canal to supply Crimea with water.

“They still have not taken control of a number of the big cities,” he said. “They might have entered them; in some cases, they’ve been repelled. But taking control of large cities is a completely different step, and they have not succeeded.”

Zelensky said in his address that resistance was working and eroding the morale of Russian invaders who were behaving like “confused children who have been used.”

Woman holding pet cat and dog

A second round of talks between Ukrainian and Russian delegations, originally scheduled for Wednesday evening, was expected to take place Thursday along the Ukraine-Belarus border. But few are holding out hope that they will be able to halt the biggest ground war in Europe in more than 75 years.

In the meantime, Ukrainian civilians face the specter of increasing terror. A close advisor to Zelensky said Russian troops had been looting, robbing and murdering civilians in territories they held.

“We need humanitarian corridors — food, medicine, ambulance, evacuation. We need active help of international organizations,” the presidential aide, Mykhailo Podolyak, said in a tweet.

The invasion has triggered the fastest-developing refugee crisis this century, with more than 1 million people fleeing Ukraine in a week, the United Nations said.

In the face of international condemnation, including a U.N. General Assembly resolution Wednesday demanding a halt to Moscow’s aggression, Russian Foreign Minister Sergei Lavrov remained defiant, saying Thursday that the U.S. and its NATO allies were responsible for provoking the war.

“They are listening to us, but they are not hearing us, and they’re trying to force upon us their own understanding of how Europe should live,” Lavrov said, comparing the U.S. to Napoleon and Hitler in its “goal to subjugate Europe.”

“I am confident that this hysteria will be over,” Lavrov added. “Our Western partners will come to their senses and will come to dialogue on one condition: of respect and taking into account each other’s interests.”

Russia is paying an increasing economic price for its war. The country’s central bank said the main stock exchange would remain closed for the fourth consecutive day Thursday, a move made to prevent a collapse of the Moscow Exchange.

Bulos reported from Kyiv and Pierson from Singapore. Henry Chu in London contributed to this report.

This story originally appeared in Los Angeles Times.