© SkyNewsA rescue worker walks through the debris in Brugnato, Italy
The initial death toll was raised as the body of a missing rescue worker was recovered from the town of Monterosso.
Officials said Sandro Usai, 40, had drowned after being engulfed by flood waters as he tried to unblock drains in the town.
The huge downpour had triggered off landslides along some of Italy's most picturesque coastline, including the Cinque Terre which is a popular destination for British holidaymakers.
Fire crews and civil protection teams worked their way through the flood-ravaged towns of Vernazza and Monterosso where cars were washed into the sea and roads turned into rivers.
Distraught mayor Angelo Betta said: ''Monterosso does not exist any more.
"We have lost electricty, gas, telephone lines and we have people missing. Everything is flooded. We need help quickly. It is just a sea of mud everywhere.''
Elsewhere dramatic TV footage from along the coast showed traditional wooden boats reduced to matchsticks as they were thrown by the force of the waves onto the rugged rocks along the shore.
Officials said that within a 24-hour period, 500mm of rain had fallen and this had led to houses collapsing and roads and train lines subsiding.
The main railway line linking Rome with the north of Italy was blocked by a landslide north of La Spezia which meant all trains to Genoa were terminating there and there was further chaos for passengers as roads were blocked.
Only fire engines and emergency vehicles were being allowed through into the minor roads in the mountains that link the worst hit villages for fear of further lethal landslides.
Helicopters will be brought in to help with the rescue effort and an air bridge set up to send in supplies with the army put on standby as part of the rescue efforts.
Those missing were in collapsed buildings or had been in cars that were washed out to see and there were fears that the death toll would grow further as the storm headed south towards Rome.
The Italian capital was hit by a similar severe thunderstorm last week which had left one dead.
This time round, three members of the same family were killed in the hamlet of Borghetto Vara near La Spezia when the house they were in collapsed.
However in a tale of amazing survival one woman was rescued after holding onto a basketball hoop for two hours.
The woman, who has not been named, was in her bar at Borghetto when it was engulfed by mud and water and she was swept into the main road for more than a kilometre before she managed to reach out for the hoop and hold on for her life.
She was eventually rescued by civil protection officials by boat, who said that she was suffering from the effects of shock and exhaustion but otherwise uninjured.
Transport links were also badly hit as roads and train lines were flooded or littered with mud and other debris and teams of workmen spent hours clearing the area so emergency supplies could be brought in as well as lifting gear.
Weather officials said the whole of northern Italy was at risk from the heavy rainstorms and flooding was also reported in Venice with the front expected to move south over the next few hours and hit Rome.
They added that a state of emergency would be declared in the regions of Liguria and Tuscany where the storms had hit with central government providing funds for the clear up.
Meanwhile police also revealed that five looters had been arrested in the village of Aulla as they picked through the wreckage of shops that had been hit by the flood waters.
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