The United States condemned the terror attacks in France, Kuwait and Tunisia on Friday but said it had seen no evidence that they were directly coordinated.
"Our thoughts and prayers are with the victims of these heinous attacks, their loved ones, and the people of all three countries," the White House said.
"We stand with these nations as they respond to attacks on their soil today and we have been in contact with appropriate counterparts in all three countries to offer any necessary support."
Aides said US President Barack Obama was being regularly briefed on the trio of Ramadan-time attacks, which spanned three continents.
"I want to make clear I think there is a common thread here of extremist activity," State Department spokesman John Kirby said.
"But I don't believe we've seen any evidence of tactical coordination ... between the attacks, or by any one or any number of individual terrorist organizations."
While there were no indications that the attacks were coordinated they came days after the Islamic State (IS) group urged supporters to carry out Ramadan attacks.
In France, a man was beheaded at an American-owned gas factory in the southeast of the country.
A gunman opened fire at tourists visiting a Tunisian beach resort, leaving at least 37 people dead, including foreigners.
In Kuwait City, a suicide bomber blew himself up during prayers at a Shiite mosque killing more than two dozen people, in an attack claimed by the Islamic State group.
UN Secretary-General Ban Ki-moon strongly condemned the "appalling" attacks and said those responsible "must be swiftly brought to justice."
European leaders condemn attack
European leaders also condemned the "heinous" attacks, vowing to maintain a united front against "barbarism".
French President Francois Hollande and his Tunisian counterpart Beji Caid Essebsi expressed their solidarity against the "scourge" of terrorism.
He also announced he was raising the security level to the highest possible in the Lyon region, where the gas factory attack took place.
Among his fellow 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.
Spain, which shares a border with southwestern France, swiftly raised its terror alert level from medium to high.
German Chancellor Angela Merkel said the attacks "show the challenges we face when it comes to fighting terrorism and Islamist extremism" while Britain's Prime Minister David Cameron called the attacks the fruit of "perverted ideology".
The EU foreign policy chief Federica Mogherini after the summit 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."
Italy's Prime Minister Matteo Renzi said the attack in France "confirms that beyond the known battle fronts there are small, very well organised groups".
Czech President Milos Zeman described Islamic State as "a cancer," calling for its training camps to be destroyed.
Outside of Europe, Israeli immigration minister Zeev Elkin urged French Jews to flee to the Jewish state. "Come home! Anti-Semitism is rising, terror is increasing," he warned.
Muslim clerics condemn attacks
Muslim clerics also condemned that attacks, using some of the strongest language to do so.
A task force against extremism set up by Egypt's mufti, the government's interpreter of Islamic law, said that attacks had done untold damage to the image of Islam "far more than what anyone else has done, whether Muslim or non-Muslim",
Prominent Sunni cleric Yusuf al-Qaradawi suggested that the militants were worse than "beasts".
"Beasts don't kill other animals except for what they need to eat, but some people never get their fill from murder and blood," he wrote on Twitter.
Canadian Prime Minister Stephen Harper said he was "both saddened and angered today to learn of the heinous terrorist attacks".
The Argentinian, Mexican and Brazilian governments were also among those strongly condemning the attack.
EU head Donald Tusk said that the attack in Tunisia affected foreign tourists but also "the security of the whole region and, in the longer term, the security of Europe."