The city of Kyiv was rocked by explosions early Thursday as Ukrainians fled their homeland and Russian troops continued their assault on cities across the country.

The Russian barrage had crippled Kherson on Wednesday and Moscow claimed its forces had taken control of the port city.

The claim was contested by a US defense official, who said on condition of anonymity that the Black Sea port was “very much a contested city.”

Kherson Mayor Igor Kolykhaev said Russian soldiers in the city were not being met with resistance from Ukrainian forces as it enacted a strict curfew and ordered civilians not to provoke troops.

“We don’t have any Ukrainian forces in the city, only civilians and people here who want to LIVE,” Kolykhaev wrote on Facebook.

“These are not warriors of a superpower,” he said of Russian troops who had come to the city’s administration building. “These are confused children who have been used.”

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“The flag flying over us is Ukrainian,” he wrote.

Fighting in the port city of Mariupol had been constant, officials told an independent Russian news agency, as officials cracked down on free speech in Moscow.

Mariupol’s power and water supplies have since been cut off.

“We cannot even take the wounded from the streets, from houses and apartments today, since the shelling does not stop,” Mayor Vadym Boychenko said.

Airstrikes continued to target Kharkiv, Ukraine’s second-biggest city. At least 21 people were killed Wednesday, officials said.

Ukraine announced 34 civilians were killed in the Kharkiv region over a 24-hour period from March 2 to 3.

A missile struck a Bangladesh-owned cargo ship on Thursday, killing one crew member. The ship was docked at the port of Olvia.

Ukraine forces shot down multiple planes, President Volodymyr Zelensky’s office said as it compared the resistance to the Russian defense of Stalingrad in World War II.

Airstrikes posed a danger to Ukraine’s 15 nuclear reactors, according to the UN nuclear watchdog agency, as an official said he was “gravely concerned.”

“The city is united and we shall stand fast,” Kharkiv Mayor Igor Terekhov told the BBC.

Meanwhile, as Ukraine shot down a missile near Kyiv’s central train station, the massive Russian convoy headed to the capital remained stalled as elderly volunteers manned checkpoints.

“In my old age, I had to take up arms,” said Andrey Goncharuk, 68. He said the fighters needed more weapons, but “we’ll kill the enemy and take their weapons.”

The convoy remained plagued by fuel and food shortages, a predicament that was hammered home by a viral video of a starving young Russian soldier being fed by compassionate Ukrainians.

Zelensky praised the resiliency of his country in a taped address to the nation Thursday.

“We are a people who in a week have destroyed the plans of the enemy,” he said, noting the low morale of the Russians. “They will have no peace here. They will have no food. They will have here not one quiet moment.”

Russia for the first time reported its war casualties, saying 500 troops were killed and 1,600 wounded. The numbers were far lower than the 5,000 Russian deaths reported by Western intelligence, but an indicator of the strong resistance the invaders faced. In comparison, fewer than 2,500 American troops were killed during a 20-year occupation of Afghanistan.

Ukraine said more than 2,000 civilians had been killed. The death toll was not independently verified.

More than a million people had fled the Eastern European country, creating “the biggest refugee crisis this century,” the UN High Commissioner for Refugees said.

Talks between Ukraine and Russia are expected to resume Thursday in Belarus, although there appeared to be little common ground between the occupying forces and the democratic former Soviet republic.

Russia accelerated its steps to subvert independent reporting on the invasion, censorship that the US categorized as a “full war on media freedom and the truth.”

President Vladimir Putin repeated false claims Thursday that his war was motivated by “self-defense against NATO expansion,” as Foreign Minister Sergei Lavrov put would-be intervening countries on notice that “a third world war could only be nuclear” in an interview with Al-Jazeera.

In Manhattan, the UN General Assembly, in its first emergency session since 1997, approved a non-binding resolution calling on Russia to retreat. The vote passed 141-5 with 35 abstentions. Russia, Belarus, Syria, North Korea and Eritrea were the only countries to reject the measure.

With AP wires