Poltava, Ukraine - President Joe Biden condemned the Russia's "deplorable attack" on the Ukrainian city of Poltava, which killed at least 51 people and wounded hundreds more Tuesday.

Ukrainian President Volodymyr Zelensky vowed to hold what he called "Russian scum" accountable, while rescuers worked to clear the rubble.

"According to the information available now, this Russian strike killed 51 people," he said in his evening address.

"The number of injured is 271. We know that there are people under the rubble of the destroyed building. Everything is being done to save as many lives as possible," Zelensky added.

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Joe Biden vowed the US would continue military aid to Kyiv, "including providing the air defense systems and capabilities they need to protect their country".

The strike triggered anger on Ukrainian social media after unconfirmed reports said it had targeted an outdoor military ceremony, with many blaming reckless behavior from officials who allowed the event to take place despite the threat of Russian attacks.

Zelensky said he had ordered a "full and prompt investigation into all the circumstances".

Two Russian ballistic missiles hit the hospital and educational institution, partially destroying one of the buildings, Zelensky said.

"The window blew open. Dust was everywhere. I just had time to tell my sister that a rocket was flying," said Yevgeniya Chyrva, a resident in a building damaged during the attack.

The defense ministry said that the time between the alarm and the arrival of the missiles was "so short that it caught people in the middle of evacuating to the bomb shelter."

The attack came as Ukraine's leadership signalled a major government reshuffle was underway, with at least six officials submitting their resignation Tuesday.

The Minister for Strategic Industries, Minister for Justice, and Minister of Environmental Protection were among those to step down, amid what Zelensky said was a need for "new energy."

The president has ordered several reshuffles since the war began, sacking his defense minister last September after a series of corruption scandals and more recently replacing his top commander amid setbacks on the battlefield.

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The move follows another recent scandal for Ukraine's army command after a US-made F-16 fighter jet crashed in combat last week, killing the pilot.

The accident was a high-profile setback for Kyiv, which had lobbied the West to send the advanced fighter jet for months, and triggered the dismissal of the country's air force chief, Mykola Oleshchuk.