More than a dozen people have died after armed men stormed an Ivory Coast beach resort.
A spokeswoman for the Foreign Office said there is no indication at this stage that 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.
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.
Meanwhile, officials said a car bombing in Turkey's capital Ankara killed more than 30 people and wounded around 75 others.
Prime Minister David Cameron tweeted: "I'm appalled by the devastating terror attacks in Ankara and the Ivory Coast. My thoughts are with all those affected."
Foreign Secretary Philip Hammond tweeted: "My thoughts & deep condolences to everyone affected by today's #Ankara & #IvoryCoast terror attacks. Both appalling attacks on civilians."
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.
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.
A statement from travel organisation Abta said: "We are unaware at the current time if there have been any fatalities or if any British nationals are involved.
"The Foreign Office advises that British nationals should avoid the area if possible. If they are already in the vicinity, they should follow the instructions of the local security authorities.
"Following recent attacks in Mali and Burkina Faso, there is a high threat of terrorism in this area. Attacks could be indiscriminate, including in places visited by foreigners, so all British nationals are advised to remain extremely vigilant."
A group that monitors jihadist websites said al-Qaida in the Islamic Maghreb has claimed responsibility for the attack in Ivory Coast.
The SITE Intelligence Group said the Islamic extremists made the declaration in a post to its Telegram channels, calling three of the attackers "heroes" for the assault.
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.