Explosions rocked the Ukrainian capital of Kyiv early on Monday, the eve of a NATO summit, as Russia mounted its second major attack on the city in days.

President Volodymyr Zelensky of Ukraine, who is expected to attend the NATO summit in Turkey, had warned that Russia was preparing “a new massive strike” against the capital.

Loud blasts shook the city hours later. The regional military administration said ballistic missiles were flying, and Mayor Vitali Klitschko urged residents to stay in shelters.

Tymur Tkachenko, the head of Kyiv’s military administration, said that at least seven people had been killed. At least two dozen others were wounded.

Thick, black smoke rose across the skyline as dawn broke. Mr. Klitschko said the emergency services were responding to multiple fires as well as at least one damaged apartment building where people were trapped.

On Thursday, Russia pounded Kyiv with missiles and drones in a nearly 12-hour assault that killed 31 people and wounded more than 100 others.

The NATO meeting begins on Tuesday in Ankara, Turkey. It is set to be dominated by the alliance’s response to the war in Ukraine.