Russia launched ballistic missile strikes on Kyiv early Thursday, local time, Mayor Vitali Klitschko said, urging residents to seek shelter as explosions were heard across the Ukrainian capital, according to Reuters.

Citing a witness, the outlet reported the sounds of multiple explosions in Kyiv. The Ukrainian Air Force also said Russia was attacking the capital with ballistic missiles, Reuters said.

The strikes came hours after Ukrainian President Volodymyr Zelenskyy warned that Russia was likely preparing a major attack.

Zelenskyy also said earlier Wednesday that Ukraine's ability to protect its citizens depends on its allies' willingness to provide additional air defense systems, including anti-missile defenses.