A gunman disguised as a holidaymaker has killed at least 37 people, including five Britons, in an attack on a popular tourist resort.

Terrified sunbathers ran for their lives as the attacker, dressed in shorts and hiding his Kalashnikov inside an umbrella, opened fire on the beach in the town of Sousse, Tunisia.

He then entered the Imperial Marhaba hotel through the swimming pool area, shooting people as he went and also threw an explosive, witnesses said.

Tourists ran from the sea and barricaded themselves in their hotel rooms after gunfire erupted, while medics used sunloungers to carry victims still in their swimming costumes.

Foreign Secretary Philip Hammond confirmed at least five Britons had died and warned the death toll could rise.