"At the moment there are five dead," a military source said on condition of anonymity after the assault in the resort popular with Westerners.
An AFP photographer said he saw seven bodies on the beach and another in the Etoile du Sud (Southern Star) hotel, one of the establishments that came under attack in the country's former French colonial capital.
The assailants, who were "heavily armed and wearing balaclavas, fired at guests at the L'Etoile du Sud, a large hotel which was full of expats in the current heatwave," one witness told AFP.
Another witness told AFP: "The shots took us by surprise and now we are staying holed up."
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A crowd of several hundred people had gathered at the entrance to Grand-Bassam's French quarter at the edge of the old town, where a dozen ambulances were on standby.
An AFP journalist saw around a dozen people, including an injured Western woman, being evacuated in a military truck.
Military vehicles carrying heavy machine guns were also heading to the scene, along with armed traditional hunters known as Dozo.
Analysts have voiced fears that Islamist attacks could spread to countries such as Ivory Coast and Senegal, and the region's US-led Flintlock military exercises that wrapped up recently focused on the need to counter jihadism.
In Burkina Faso and Mali, Al-Qaeda in the Islamic Maghreb (AQIM) claimed responsibility for deadly attacks on hotels popular with foreigners in November 2015 and in January this year.
Ivory Coast is the world's top cocoa producer. Its former president Laurent Gbagbo is currently on trial at the International Criminal Court for crimes against humanity over deadly violence that followed the disputed 2010 election.