One of the worst hit areas was the town of Olbia in the northeast of the island which saw severe flooding leaving bridges in a state of collapse.
The Mayor Gianni Giovanelli said houses across the area had been left half submerged by the floods and rescuers were still searching for possible victims.
Italian authorities have declared a State of Emergency. Prime Minister Enrico Letta, speaking on Italian Radio said this would permit rapid intervention and to make available the extra resources needed to deal with the areas devastated last. Calling what had happened a national tragedy Mr Letta also said the government was allocating 20 million euro for relief efforts. Listen to Lydia O'Kane's report