Yesterday's carnage at the popular Mediterranean resort of Port el Kantaoui came the same day a suicide bomber killed 27 people at a Shiite mosque in Kuwait and a suspected Islamist attacked a factory in France.

There was no immediate claim of responsibility for the Tunisia attack, but the Islamic State group, which Monday marks the first anniversary of its 'caliphate' straddling Iraq and Syria, said it bombed the Kuwait mosque.

Witnesses described scenes of panic after the shooting at the five-star Riu Imperial Marhaba Hotel on the outskirts of Sousse, about 140 kilometres South of Tunis.

The death toll rose to 39 late yesterday, the Health Ministry said. British Foreign Secretary Philip Hammond said in London five Britons had been killed and warned that the toll could rise.

"Because of the nature of the composition of the tourist population in this part of Tunisia, we have to assume that a high proportion of those killed and injured will have been British," he said.

A spokesman for Spain's RIU group said most of the 565 hotel guests were from Britain and Central European countries.

In Dublin, Foreign Minister Charles Flanagan said an Irish woman was among the dead. Interior ministry spokesman Mohamed Ali Aroui said, "The assailant was killed."

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.

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