A gunman disguised as a tourist with a weapon hidden in a sun umbrella has massacred tourists at a Tunisian beachfront hotel, killing 39 people.
Photo: AFP
At least 36 people were injured, some critically, and the gunman himself was shot dead by the police.
A government official said the gunman was a student previously unknown to police.
In a statement on social media, Islamic State claimed responsibility for the Tunisian attack. It had urged its followers to step up assaults during Ramadan.
Twitter accounts that support Islamic State released three photos they said showed the gunman.
A man is seen from behind walking down a street and holding an assault rifle, though his identity and the location are unclear.
Tunisians, Britons, Germans and Belgians and at least one Irish citizen were among the dead.
Tunisian President Beji Caid Essebsi has gone to Sousse's Sahloul hospital to visit the injured.
Security officials said one attacker, who had posed as a swimmer but was carrying a rifle under a parasol, was shot dead in an exchange of fire with police.
Local media reported that the second attacker had been arrested, but this has not been confirmed.
One of those killed was an Irish woman, Irish Foreign Minister Charles Flanagan said.
A British man on holiday told the BBC that he heard the attack on a neighbouring hotel.
From his room, he saw a man with a pistol but did not know whether this was an attacker or a member of the security forces.
Photo: AFP
Tourists react in the Imperial hotel at the resort town of Sousse. Photo: AFP
The Hotel Imperial Marhaba was named as one of the hotels close to the attack.
Briton Glenn Leathley told the BBC his daughter had been at the scene and rang him to say "there's gunfire on the beach".
Another British holidaymaker, Steve Johnson, told the BBC: "We were just laying on the beach as usual and... we heard what we thought at first was fireworks.
"But it was soon pretty obvious... that it was firearms that were being discharged and people screaming and starting to run."
One image circulating on social media appeared to show a man lying face down in the sand with what looks like blood around his head.
The Islamic State militant group had called on its followers to increase attacks during the Islamic fasting month of Ramadan, but no-one has yet said they were behind this attack.
The UK Foreign Office said the British embassy in Tunis was sending a crisis team to the area.
"Any British nationals in these hotels or nearby should remain indoors, and contact their tour operator and the Foreign Office. For security reasons they should not advertise their location on social media or when speaking to journalists," the FCO said in its updated travel advice.
The Belgian foreign ministry is advising against all travel to Tunisia and the Belgian Jetairfly airline has announced it is cancelling all flights to Tunisia because of the attack.
A Tunisian security member stands next to a swimming pool at the resort town of Sousse following the attack. Photo: AFP
A spokeswoman for the Thomson and First Choice tour operators said: "We are working closely with our teams in Tunisia and the relevant authorities to determine exactly what has happened and provide assistance to those affected."
In March militants killed 22 people, mainly foreign tourists, in an attack on a museum in the capital Tunis.
Tunisia has seen militant Islamists gain strength since the overthrow of long-serving ruler Zine al-Abidine Ben Ali in a popular uprising in 2011.
Democratic elections after Ben Ali's removal saw the moderate Islamist Ennahda party take power before the secularist Nidaa Tounes government won a parliamentary poll in October.
However, neither party has been able effectively to combat Islamist violence made worse by a raging conflict in neighbouring Libya and by Tunisian fighters returning home after going to join Islamist campaigns in Iraq and Syria.
-BBC/ Reuters