The strike hit the city center, officials said. Two women, ages 20 and 61, and two men, ages 60 and 76, were wounded.
Two more men, ages 45 and 42, were injured while near one of the impact sites.
Authorities also reported damage to buildings and vehicles. The full extent of the damage is being assessed.
Public broadcaster Suspilne published photos showing the aftermath of the Russian strike on Sumy.
In addition, infrastructure was damaged in Konotop following enemy shelling, Suspilne reported, citing Mayor Artem Semenikhin.
Overnight, Russia carried out a large-scale missile and drone attack on Ukraine, including western oblasts. Explosions were reported in Odesa, Dnipro, Kropyvnytskyi and Burshtyn in Ivano-Frankivsk Oblast.
According to Ukraine’s Air Force, air defenses overnight destroyed 25 missiles and 367 Russian drones.
President Volodymyr Zelenskyy said the combined Russian strike was deliberately planned to inflict maximum damage on Ukraine’s energy sector.
In Odesa, the attack caused extremely serious damage to energy infrastructure. In Ivano-Frankivsk Oblast, heat supply was temporarily suspended in one community.