A Russian ballistic missile hit a cargo ship in the port of Odessa, according to Ukrainian authorities.
"Unfortunately, four people were killed, Syrian citizens. At the time, the ship was loading wheat for export to Algeria. It was completely civilian," writes government official Oleksij Kuleba on social media.
Earlier, Kyiv's mayor Vitalij Klytjko had warned of an attack on the capital.
"Air defense forces are active in the city. Stay in shelters," wrote Klytjko around midnight Swedish time. Barely an hour later, the danger was over.
In Kharkiv in northeastern Ukraine, a Russian attack drone crashed between residential buildings late on Tuesday evening, according to the city's mayor Ihor Terechov. No one was physically injured.
The region of Dnipropetrovsk was also subjected to Russian drone attacks. According to Governor Serhij Lysak, there are no reports of personal injuries, but several residential buildings were damaged.
The attacks come hours after Ukraine and the US announced that they support a proposal for a total ceasefire for 30 days, provided that Russia accepts this.
The ball is now in Russia's court, said US Secretary of State Marco Rubio after the negotiations in Saudi Arabia.
