More than 100 police and emergency personnel were deployed to the scene of the blast on Monday evening.
Harri Richie, who lives around 100m away from the targeted building, told the BBC she had heard an “unbelievably loud explosion” from the underground car park she was in.
She then went up to her 11th floor apartment, where she said she saw emergency services “dragging two people out [from the building] who looked badly injured”.
Emergency services arrived around five minutes after the explosion, she said, adding that there was a helicopter overhead throughout the night.
“This is the first time in history, to my knowledge, that such an act has taken place in the principality,” Mirmand said.
Monaco’s Prince Albert II described the incident as a “heinous crime” and a “shock to the entire Monaco community”.
Citing anonymous sources, French newspaper Le Figaro reports that the three victims seriously hurt in the attack are Yermolaiev, his partner and their 13-year-old son.
Yermolaiev, 58, is a wealthy real estate developer from Dnipro, Ukraine’s fourth-largest city, who has been living in Monaco.
He is now a Cypriot citizen after renouncing his Ukrainian citizenship in 2019.
He has big interests in the wine and alcohol business in Russian-annexed Crimea, and since 2023 has been the subject of sanctions imposed by the government in Kyiv.
He was named the 39th richest Ukrainian by Forbes magazine in 2020, with a fortune of $230m (£173.8m).