Updated 1- Emergency crews are working to reach remote parts of flood-ravaged Sardinia after a torrential rainstorm killed at least 17 people, collapsed bridges and swept cars away.

Italy's civil protection chief, Franco Gabrielli, said one person remained unaccounted for and that the death toll could still rise as crews reach isolated areas in the countryside where some homes are submerged.

The island, famed for crystal-clear beaches and dry Mediterranean climate, was inundated with 16in (400mm) of rain in 24 hours, he told Sky TG24.

Olbia Mayor Gianni Giovanelli said the city had been destroyed by the "apocalyptic" storm, with bridges felled by gushing, muddy rivers and water levels reaching 3m in some places.

Premier Enrico Letta convened his Cabinet this morning to declare a state of emergency to free up funding and resources.

Sardinia Governor Ugo Cappellacci said the dead included a family of four, reportedly of Brazilian origin.

Local newspaper L'Unione Sarda said one policeman helping to escort an ambulance died when the car he was travelling in was submerged in the collapse of a bridge in Dorgali.

In hard-hit Gallura, three people died when their car was swept away in the collapse of another bridge, it said.