Russian drones hit a gas truck that was making deliveries to households in a border village, Ukraine's national police force said on Telegram.
"The truck exploded and residential buildings caught fire." Three people were killed in the blast, including a child born in 2018, the police said.
Four others were hospitalised, including two children, aged four and 13. The children were in a serious condition, according to regional governor Vyacheslav Chaus.
Police posted photos of a burned out gas truck on the side of a village track and nearby houses destroyed, with fires raging in the gardens.
The army said three first-person view (FPV) drones were used in the attack. FPV drones are controlled remotely by human pilots who can see live images from them.
Part of the Chernigiv region was briefly occupied by Russian forces after they invaded the country from the north at the start of the conflict.