The body is being investigated after at least 47 people were killed in an attack not believed to be near any other military targets.
It caused damage to a high-rise apartment building, a hospital and several other residential and commercial buildings, one of which contained a pharmacy.
Human Rights Watch interviewed by phone three witnesses to the attack, including a doctor and two other Chernihiv residents, as well as two additional Chernihiv residents with knowledge of the attack.
They also verified and analysed 22 videos and 12 photographs taken during the attack and its aftermath.
The incident is the latest in a series of attacks by Vladimir Putin’s forces that are now being labelled war crimes.
Even in conflict there are certain rules to be followed, contained in treaties called the Geneva Conventions and a string of other international laws and agreements.
They mean civilians cannot be deliberately attacked, nor can infrastructure that is needed for them survive.
Some weapons are also banned due to the level of suffering they cause such as anti-personnel landmines and chemical or biological weapons.
Those wounded or sick must also be cared for, including injured soldiers who have protected rights as prisoners of war.
Torture and genocide are also banned, as are offences such as murder, rape or mass persecution of a group, falling under the bracket of "crimes against humanity".
Taking place during an agreed ceasefire, three people including a child were killed, with 17 staff and patients injured.
Ukraine president Volodymyr Zelensky revealed people were trapped under the wreckage and called the attack a war crime.
Sergey Lavrov, the Russian foreign minister, told a news conference the hospital was a “legitimate target” by claiming it had been overtaken by “extremists”.
Russia has been accused of using cluster bombs in Kharkiv, something now being investigated by the ICC.
Cluster munitions open in the air and can disperse dozens hundreds of small submunitions over a large area.
The ones that do not explode on impact then act like landmines if touched.
More than 100 countries are part of an international treaty that bans the making or use of cluster bombs, but Russia and Ukraine are not.
Despite this, the use of them is still considered a war crime.
Russia also stands accused of using thermobaric weapons – also known as vacuum bombs.
The UK's Ministry of Defence said Russia had confirmed the use of the TOS-1A weapon system in Ukraine.
The weapon explodes on impact, releases a cloud of explosive material then ignites again in a blast capable of vaporising human bodies.
As well as specific weapons, there have also been reports Russian troops have targeted fleeing Ukrainian civilians.
The ICC's chief prosecutor British lawyer Karim Khan QC has said war crimes may have taken place and is now investigating.
However, even if there is evidence, any prosecutions are unlikely given Russia has not been a member of the court since 2016.