There were no immediate reports of casualties.
Kharkiv Mayor Ihor Terekhov said on Telegram that the early-morning explosions were the result of missile strikes in the centre of the city. He said that the blasts sparked fires at one of the city's medical institutions and a non-residential building, CBC reported.
The explosions came as news sources said that Moscow concentrates attacks on Ukraine on regions that joined Russia after the referendum.
It was not immediately clear what caused the Kharkiv blasts or what was hit.
Putin this week announced four regions of Ukraine as Russian territory — the Zaporizhzhia and Kherson regions in the south and the Donetsk and Luhansk regions in the east.
MNA/PR