Gunmen from the North African branch of al-Qaeda killed 16 people, including four Europeans, at a beach resort town in Ivory Coast.
This is the latest in a string of deadly attacks across West Africa.
Six shooters targeted hotels on a beach at Grand Bassam, a weekend retreat popular with westerners about 40km east of the commercial capital Abidjan, before being killed in clashes with Ivorian special forces.
A French man was killed in the attack, according to a French foreign ministry spokesman. The nationalities of the other dead was not yet known, but four were European, one officer said during a briefing.
A Reuters reporter saw the bodies of three white people at Grand Bassam's Chelsea Hotel and another in the Hotel Etoile du Sud next door.
Al-Qaeda in the Islamic Maghreb (AQIM), which has carried out other recent attacks in the region, claimed responsibility for the shootings, according to the US-based SITE intelligence monitoring group.
Gunmen dressed in black opened fire while people were eating and drinking at the beachside bars and restaurants or swimming in the ocean.
Security forces moved to evacuate the area surrounding the beach. Bullet holes riddled vehicles nearby and some windows had been shot out.
"They started shooting and everyone just started running.There were women and children running and hiding," said witness Marie Bassole.
"It started on the beach. Whoever they saw, they shot at."
Barely two months ago, Islamist fighters killed dozens of people in a hotel and cafe frequented by foreigners in neighbouring Burkina Faso's capital, Ouagadougou. Gunmen also attacked a hotel in the Malian capital Bamako late last year.
Both of those attacks were claimed by AQIM, raising concern that Islamist militants were extending their reach beyond their traditional zones of operation in the Sahara and arid Sahel region.
Though previously untouched by Islamist violence, Ivory Coast, French-speaking West Africa's largest economy and the world's top cocoa producer, has long been considered a target for militants. It has been on high alert since the Ouagadougou attacks.
French President Francois Hollande pledged support, denouncing the shootings as a "cowardly attack".
"France will bring its logistical support and intelligence to Ivory Coast to find the attackers. It will pursue and intensify its cooperation with its partners in the fight against terrorism," Mr Hollande said in a statement.