National security correspondent Greg Miller discusses the impact of three terrorist attacks in France, Tunisia and Kuwait after an Islamic State leader called to make the month of Ramadan a time of "calamity for the infidels." (McKenna Ewen/The Washington Post)

Assailants beheaded, bombed and gunned down victims on three continents Friday, killing more than 60 people and raising fears that a global surge of terror strikes could be imminent.

There was initially no reason to believe the disparate attacks — at a factory in France, a beach resort in Tunisia and a mosque in Kuwait — were connected.

But then the Islamic State asserted responsibility for two of them, first the bombing in Kuwait in which 25 died and later, in a separate statement, the assault on the beach in Tunisia, which killed 39.

The second statement contained a warning that more attacks soon will follow: “Let them wait for the glad tidings of what will harm them in the coming days, Allah permitting,” it said, referring to the “apostates” who had been the target of the assault.

The three incidents followed an appeal Tuesday from the Islamic State’s spokesman, Abu Mohammed al-Adnani, for Muslims to mark the holy month of Ramadan by carrying out acts of “jihad,” or holy war.

“Make Ramadan a month of disasters for the kuffar,” meaning infidels, he said in the audiotaped address. He promised followers “tenfold” rewards in heaven if they died in such acts during the holy period, associated by most Muslims with fasting, prayer and peaceful reflection.

The attacks suggested that some may have heeded his words.

About 9:30 a.m. in the quaint town of Saint-Quentin-Fallavier in southern France, a deliveryman crashed a vehicle into a shed containing gas cylinders at an American-owned factory, causing an explosion. After the driver was caught by firefighters, police found a severed head on the factory fence flanked by two flags bearing Arabic inscriptions.

Minutes later and 3,000 miles away, a man wearing a suicide belt walked into a Shiite mosque in Kuwait City and detonated his explosives among worshipers gathered for Friday prayers, killing 25.

Two hours passed before at least one gunman burst into a Mediterranean beach resort in the Tunisian town of Sousse and randomly opened fire on bathers lounging under beach umbrellas, killing 39.

The Islamic State asserted responsibility for the attack in Kuwait, saying in a statement circulated on social media accounts that one of its members, Abu Suleiman al-Mowahid, targeted the mosque because it had been used to try to convert Sunni Muslims to the Shiite branch of Islam.

It was too early to say whether the Islamic State was connected to the French attack or whether the strike was conducted on behalf of the Islamic State or was inspired by its propaganda. A Pentagon spokesman, Col. Steve Warren, said U.S. officials are investigating possible links.

But the timing and geographical scope of the violent acts appeared likely to play into the Islamic State’s narrative that it is posing an ever-greater threat to global security, analysts said.

“For ISIS, terror is a strategy, a way to keep conveying a sense of expansion,” said Emile Hokayem, an analyst with the London-based International Institute for Strategic Studies, using an acronym for the extremist group. “This is not a movement that’s on its last legs. It’s still there, seeking to impose and shape the agenda and be at the center of the conversation.”

In France, the gruesome killing caused jitters in a country still reeling from the Charlie Hebdo slayings in January, in which two gunmen mowed down staffers at a satirical newspaper in Paris.

French prosecutor François Molins said at a news conference that the man detained in Friday’s attack, identified as Yassin Salhi, 35, had periodically drawn the attention of French intelligence services between 2011 and 2014 because of his links with ultraconservative Muslims, known as Salafists, in Lyon. Security services had filed reports between 2006 and 2008 on the man’s radicalization, he said.

The victim found beheaded at the factory was the 54-year-old manager of the transportation firm that employed Salhi, the prosecutor said. In addition to the beheading, there were also two injuries in the explosion at the factory operated by Air Products, a global gas and chemical company based in Allentown, Pa.

French President François Hollande called it “a pure terrorist attack, especially inasmuch as a corpse has been found, decapitated with a message.”

He summoned security chiefs and placed security agencies in southeastern France on a state of high alert.

Tunisia also was still reeling from a recent terrorist attack — the assault by gunmen in March at the Bardo museum in the capital, Tunis, in which 22 people died. The bloodshed on the beach in Sousse is expected to further dent the North African country’s vital tourism industry.

Witnesses described scenes of chaos as a gunman opened fire with an automatic rifle, sending sunbathers scrambling for cover amid beach umbrellas and sun beds. Tunisian authorities said the assailant was killed, and it was unclear whether more than one attacker was involved.

“A state of panic,” said Tunisian journalist Moez Ben Gharbiya, describing the scene from the seaside town, a popular spot for European tourists about 90 miles south of Tunis.

The bombing in Kuwait fit a recent pattern in which the Islamic State has been targeting Shiite mosques in Saudi Arabia and Yemen.

The tactic echoes the way in which an earlier iteration of the group provoked sectarian strife in Iraq by relentlessly bombing Shiite mosques, and this appears to be the goal now, Hokayem said.

“By going after Shiites in Saudi and Kuwait, ISIS is playing a sophisticated game where it thrives off of existing sectarianism in the Sunni world,” he said.

Kuwaitis, however, rallied behind the Shiites, a small but widely accepted minority in the tiny nation. The country’s emir immediately visited the mosque, and Kuwaitis lined up to donate blood to the injured, who numbered more than 200, according to media reports in Kuwait.

“This criminal act on one of the houses of God is a desperate and wicked attempt to divide the unity of the Kuwaiti people, and it comes amid threats faced by the entire region,” said Crown Prince Nawaf al-Ahmad al-Jaber al-Sabah in a statement on Kuwaiti state television.

World leaders elsewhere denounced the attacks.

The United States “condemns in the strongest terms the terrorist attacks” in the three countries, a White House statement said.

British Prime Minister David Cameron tweeted that he was “sickened by the attacks in Tunisia, France and Kuwait,” and he summoned an emergency meeting of his security chiefs to assess the heightened threat.

Read more:

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Today’s coverage from Post correspondents around the world

Brian Murphy in Washington, Mustafa Salim in Baghdad, Hugh Naylor in Beirut and Karla Adam in London contributed to this report.