Zelensky called it "another massive attack against our country," saying one person was killed in the southern city of Mykolaiv, and two were killed in the capital Kyi, where part of the city lost power.

The head of the Ukrainian armed forces said that Russia fired 44 missiles and 20 drones at Ukraine on Wednesday in a wave of morning aerial attacks across the country.

"The enemy carried out several strikes on the territory of Ukraine, using various means of air attack -- attack drones, cruise, ballistic and anti-aircraft guided missiles ... 44 air targets were destroyed: 29 missiles and 15 attack drones," Ukraine's commander-in-chief Valery Zaluzhny said in a post on Telegram.

The mayor of Mykolaiv, Oleksandr Senkevich, said that one man died from severe injuries after the attack stripped roofs off 20 houses and damaged gas and water pipes in the port city.

Loud explosions were heard in the capital Kyiv by AFP journalists.

Kyiv Mayor Vitali Klitschko said that six people had been injured in the city.

Fires were burning on several floors of an 18-story apartment block in the city's southern Golosiivskyi district, where three were hospitalized, Klitschko said.

The attack came as EU diplomacy chief Josep Borrell was visiting the capital.

He went to an air-raid shelter in his hotel during the attack, an AFP journalist saw.

Three people were also injured in Kyiv's Dnipro district, a residential area on the eastern bank of the Dnipro River, where missile fragments damaged high-voltage lines, Klitschko said.

An energy company said the Dnipro district was partially without power and repair work would begin after the all-clear.