File Photo: Cars swept away by flooding in Alhambra de la Riviera II, a neighbourhood of Cocody, in the district of Abidjan, taken on June 25, 2020. AFP
About 30 people had to be rescued and one taken to hospital, the fire brigade said in a statement posted on social media.
"We have been deployed since 3:00 am (0300 GMT) at several flooded areas. The provisional toll: four deceased victims (children)," they said, adding their rescue efforts were still ongoing.
Heavy rain fell through the night, flooding many neighbourhoods of Abidjan and leaving several key roads unusable.
Residents posted images on social media showing the extent of the flooding in their homes or neighbourhoods and calling for help.
Last week, six people died after torrential rain triggered a landslip in the city's western neighbourhood of Mossikro.
Landslips during the rainy season are a notorious risk in Abidjan, a fast-growing city of five million people.
Previous accidents claimed 18 lives in June 2018 and 13 in June 2020.