European leaders condemned Friday's "heinous" suspected Islamist attack on a gas factory in France and massacres in Tunisia and Kuwait, vowing to stay united against "barbarism".
One person was decapitated near Lyon in southeastern France while in Tunisia gunmen killed at least 27 people in a beach resort and in Kuwait a suicide bombing at a mosque killed 13.
French President Francois Hollande and his Tunisian counterpart Beji Caid Essebsi expressed their solidarity against the "scourge" of terrorism.
Among European Union leaders gathered for a summit in Brussels, Spanish Prime Minister Mariano Rajoy was one of the first to react to news of the attack in France.
"Barbarism will always be confronted by unity among democrats," he wrote in a message on Twitter.
"In this battle, all good people must be united, whatever their beliefs," he added later at a news conference.
German Chancellor Angela Merkel said the attacks "show the challenges we face when it comes to fighting terrorism and Islamist extremism".
She expressed her "solidarity and sympathy" with French President Francois Hollande. Merkel's Foreign Minister Frank-Walter Steinmeier called the attack in France a "heinous murder".
Britain's Prime Minister David Cameron called a meeting of a government emergency committee to discuss the attacks.
"Our hearts all go out to the victims of these appalling terrorist attacks," Cameron said, branding them the fruit of "perverted ideology".
Rajoy too said Spanish officials would hold a meeting of their anti-jihadism emergency committee in Madrid.
A severed head was pinned to the gate of the factory near Lyon and several other people were injured in what Hollande described as a "terrorist attack".
That killing came nearly six months after Islamist attacks in and around Paris that killed 17 people in January, which prompted an outpouring of international sympathy.
In the Tunisian resort district of Sousse on Friday, a gunman opened fire at tourists on the beach at a hotel, leaving at least 27 people dead, including foreigners.
Authorities there also branded that massacre a "terrorist attack".
The French and Tunisian leaders "expressed their solidarity in the face of terrorism", the French presidency said in a statement.
The shooting in Tunisia came just months after an attack on a museum in Tunis killed 21 foreign tourists and a policeman in March.
In Kuwait City, a suicide bomber blew himself up during Friday prayers at a Shiite mosque, killing at least 13 people in an attack claimed by the Islamic State group.
The president of the European Commission Jean-Claude Juncker said he shared "the grief of France and two other countries", Tunisia and Kuwait.
Italy's Prime Minister Matteo Renzi said he had expressed his "solidarity directly to Francois Hollande" over the attack in France.
He said that attack "confirms that beyond the known battle fronts there are small, very well organised groups."
Renzi set up a crisis group to find out whether any Italians were among those killed in the attack in Tunisia.
Romania's Foreign Minister Bogdan Aurescu on Twitter called for the enhancing of "global efforts to act against, prevent and deter terror. We need a court against terrorism."
The EU foreign policy chief Federica Mogherini called for the Arab world and Europe to stay united.
"Arabs, Europeans, Muslims, non-Muslims, we are together, in the same boat," she said.
"The response will be more unity and expressing very clearly, as an alliance of civilisations, that there can be no way in which a religion be misused to tear us apart."