More than a dozen people have died after armed men stormed an Ivory Coast beach resort.
A spokeswoman for the Foreign Office said officials were "urgently" trying to establish whether any British nationals had been caught up in the incident.
The Ivory Coast's president Alassane Ouattara said 14 civilians, six attackers, and two special forces operatives were killed in the attack on three hotels in Grand-Bassam, a popular weekend destination for both Ivorian nationals and foreigners.
Photos posted to social media apparently taken at the scene showed bodies sprawled on the beach.
Officials urged the public to remain calm after the incident in the south-eastern beach resort, about 25 miles east of Ivory Coast's economic centre, Abidjan.
The beach setting of the incident bears a resemblance to the attack in the Tunisian resort of Sousse last June in which 30 Britons were among 38 tourists killed.
Bournemouth footballer Max Gradel, who is from the Ivory Coast, tweeted: "May God protect my lovely country in this hard moment Cote D'ivoire".
Josiane Sekongo, 25, who lives across from one of the town's many beachfront hotels, said she ran outside when she heard gunshots and saw people running away from the beach.
An American embassy delegation was in Grand-Bassam on Sunday, but the US Embassy in Abidjan said it is monitoring the situation and it has no evidence that US citizens were targeted.
Attacks by extremists on hotels frequented by foreigners in two other West African countries, Mali in November and Burkina Faso in January, killed dozens of people and indicated that extremist attacks are spreading from North Africa.
The historic town of Grand-Bassam is a Unesco World Heritage site.
The travel advice for Ivory Coast on the Foreign Office website warns against all but essential travel to certain parts of the country.
It says: "There is a high threat from terrorism. You should be vigilant after recent attacks in Mali and Burkina Faso. Attacks could be indiscriminate, including in places visited by foreigners."
For Grand-Bassam, the website says people should check travel advice before travelling.
The advice was updated on February 9 and was still said to be current on March 13.
Security forces and members of the Ivorian Red Cross are clearing the bodies.
Witness Marcel Guy saw at least four gunmen with Kalashnikov rifles on the beach. He said one approached two children, and spoke in Arabic.
One child knelt and prayed, but the other was shot dead.