The SITE Intelligence Group on Saturday reported that the Islamic State group has claimed credit for the attack at a Tunisian resort that killed at least 38 people.
The group said in a news release that the extremist group made the claim on its Twitter account Friday and identified the gunman as Abu Yahya al-Qayrawani.
Apart from the attack in Tunisia, a suicide bomber targeted a mosque in Kuwait and a decapitated head was displayed on the fence of a gas factory in France in a series of Islamist assaults Friday that have claimed at least 66 lives.
The attacks were not apparently coordinated, but came after the Islamic State group urged supporters to carry out attacks during Ramadan.
At least 38 people, including foreign tourists who had been sunbathing and swimming, were shot dead at the packed Tunisian Mediterranean resort of Port el Kantaoui in Sousse after a man pulled out a gun hidden inside a beach umbrella.
The majority are British," Prime Minister Habib Essid told a news conference. "After them come the Germans, then the Belgians and then other nationalities," he said, adding that there were also French among the victims.
Secretary of State for Security Rafik Chelly told Mosaique FM the gunman was a Tunisian student unknown to the authorities.
"He entered by the beach, dressed like someone who was going to swim, and he had a beach umbrella with his gun in it. Then when he came to the beach he used his weapon," Chelly said.
British tourist Ellie Makin saw the attack unfold."All I saw was a gun and an umbrella being dropped," she told ITV television.
Twitter accounts that support Islamic State released three photos of someone they said is the gunman. News agencies could not independently verify the authenticity.
The photos provide a view from the rear of a man walking down a street and holding an assault rifle. The Twitter accounts praised him, wishing him entry to paradise. Reuters could not independently confirm the authenticity of the photographs.
The shooting was the worst in modern-day Tunisia and followed a March attack claimed by IS on Tunis's Bardo National Museum that killed 21 foreign tourists and a policeman.
IS claims Kuwait bombing
IS also claimed the suicide bombing at a Shiite mosque in a rare attack on Kuwait in which 27 people were killed.
Kuwait's interior ministry said an unspecified number of suspects were held for questioning in connection with the attack that shocked the society of this small oil-rich Gulf state. No details were provided.
The Islamist bloodshed comes on the second Friday of the holy month of Ramadan in which Muslims observe a fast from dawn to sunset every day.
A suicide bomber entered a mosque in the capital as Muslims took part in Friday prayers, killing 27 people and wounded more than 200.
It was the Gulf state's first such attack in nearly a decade.
The IS-affiliated group in Saudi Arabia, calling itself Najd Province, said one of its militants had carried out the bombing on a mosque it claimed was spreading Shiite teachings among Sunni Muslims.
IS, a radical Sunni Muslim group, considers Shiites to be heretics. Najd Province has claimed responsibility for several other attacks on Shiite mosques in neighbouring Saudi Arabia.
Kuwait's emir, Sheikh Sabah al-Ahmad al-Sabah, said after visiting the site of the attack that it was "a desperate and evil attempt targeting Kuwait's national unity".
Severed head displayed in France
In France, at least one extremist rammed a car into a factory owned by US firm Air Products near France's second city of Lyon.
The severed head of a businessman identified as the suspect's boss by police, was found attached to the gates of the factory.
The alleged attacker, named by police as Yassin Salhi, appeared to have been trying to blow up the plant by releasing explosive gases when he was caught.
French President Francois Hollande said inscriptions were found on the headless body, while Interior Minister Bernard Cazeneuve said Islamist flags were displayed around the head, without saying if they were those of IS.
"The intent was without doubt to cause an explosion. It was a terrorist attack," said Hollande. Cazeneuve said Salhi was known to have links to a radical form of Sunni Islam.
The act of beheading has become a hallmark of the Islamic State group which has taken over large parts of Iraq and Syria and rallied supporters around the world to carry out attacks in their countries.
The Islamic State group marks June 29 as the first anniversary of its self-declared "caliphate" straddling Iraq and Syria.
On Tuesday, Islamic State group spokesman Abu Mohammed al-Adnani called for Muslims to engage in jihad and become martyrs during Ramadan.
"The best acts that bring you closer to God are jihad, so hurry to it and make sure to carry out the invasion this holy month and be exposed to martyrdom in it," Adnani said in an audio message posted online."These are your weapons and this is Ramadan."
The IS militants were also accused by the Syrian Observatory for Human Rights of killing 164 civilians in an offensive on the Kurdish town of Kobane. The terror group had been dramatically ousted in January by Kurdish militia backed by US-led air strikes after four months of heavy fighting.
France and Spain raised their alert level after the attacks, and Britain increased security at public events.
The White House condemned what it described as "heinous attacks" in the three countries, adding: "We stand with these nations as they respond to attacks on their soil today."