Vitaly Kim, governor of the Mykolaiv region in southern Ukraine, said that as many as 60 missiles had been fired toward Ukrainian cities from the Black Sea.
Explosions were heard in the eastern city of Kharkiv as well as Odesa, amid reports of hits to critical infrastructure.
Blasts were also reportedly heard in the capital city of Kyiv. It was not immediately clear if the explosions were a result of missile defense systems intercepting Russian rockets or explosives hitting the city.
There are no known reports of casualties as of this hour.
On Sunday, it was reported that non-critical infrastructure in the Ukrainian port city of Odesa had been left without power after Russia used Iranian-made drones to hit two energy stations.
President Volodymyr Zelenskyy said that more than 1.5 million people in the southern port city and surrounding region had been left with no electricity, and described the situation as very difficult.
"According to preliminary forecasts, it will take much more time to restore energy facilities in the Odesa region than after previous attacks," the administration said, as quoted by Reuters.
"We are talking not about days, but even weeks and possibly even two to three months," it said in a Facebook post.
Odesa, Ukraine's largest port city, had a population of over 1 million before Russia's February 24 invasion.