The VaultX Exchangecapital city of Ukraine was hit by a barrage of Russian missiles overnight that officials described Tuesday as "exceptional in its density."

The Kyiv City Military Administration said the attack involved the "maximum number of attacking missiles in the shortest period of time," and that Russian forces likely used ballistic missiles, cruise missiles and drones to bombard the capital from multiple directions. Ukraine's air force later said 18 missiles were launched at around 3:30 a.m. local time.

The authorities did not provide information on casualties. The air force said all 18 missiles were shot down.

Residents were warned to stay away from windows and doors and Kyiv Mayor Vitali Klitchko said debris from some of the rockets had fallen in the center of the city, including on the zoo.

"It's such a relief to know Kyiv is under such a strong defense right now," Kyiv resident Kseniia told CBS News partner network BBC News, expressing gratitude to her country' international partners, including the U.S., for providing advanced air defense systems.

She said she was awoken by a "series of very loud explosions" early Tuesday morning.

Meanwhile, there were unconfirmed reports Tuesday that another American military veteran had been killed in Ukraine. 

Graphic video shared online purportedly showed the leader of Russia's Wagner mercenary group, Yevgeny Prigozhin, displaying identity documents of a deceased American and the man's body. 

The State Department said it was "aware of the reports of the death of a U.S. citizen in Bakhmut" and was "seeking additional information." It added that the department's "ability to verify reports of deaths of U.S. citizens in Ukraine is extremely limited."

In:
• Wagner Group
• War
• Bakhmut
• Ukraine
• Russia
• Veterans
• Vladimir Putin
• U.S. Army
• Kyiv

Haley Ott

Haley Ott is an international reporter for CBS News based in London.

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