The cyclone lashed Sardinia's coast for many hours, as Alan Johnston reports

At least 18 people, including four children, have been killed in flooding on the Italian island of Sardinia after a cyclone and heavy rain.

A number of people are reported missing after rivers burst their banks. Cars were swept away and bridges collapsed.

The area around the north-eastern city of Olbia was worst-hit - in some places the water was up to 3m (10ft) deep.

Prime Minister Enrico Letta has declared a state of emergency, speaking of a "national tragedy".

Mr Letta announced that 20 million euros (£16.8m, $27m) would be allocated immediately to emergency relief efforts, with soldiers deployed in the region.

"We are focusing on essential operations: saving human lives, assisting displaced people and clearing road access," he said after an emergency cabinet meeting on Tuesday.

More than 440mm (17.3in) of rain fell in 90 minutes overnight into Tuesday morning.

Victims

A Brazilian family of four drowned when their basement flat in the town of Arzachena, in the northern part of the island, filled with water. Two children were among the dead.

Three people died when a road bridge collapsed on to their car near Olbia, according to local media.

In a separate incident, a mother and her daughter were found dead in their car after it was swept away by floods.

Among the victims was a police officer who died after a bridge collapsed as he tried to escort an ambulance.

Hundreds of people across the Mediterranean island have been moved from their homes because of the flash flooding caused by Cyclone Cleopatra.

"We're at maximum alert," Giorgio Cicalo, an official from Sardinia's civil protection authority, told Italy's Rai TV.

"We haven't seen a situation as extreme as this, perhaps for decades - especially because it's been across the whole island."

'Apocalyptic'

Sardinian Governor Ugo Cappellacci told Italian TV that the situation on the island was "dramatic".

Meanwhile Olbia Mayor Gianni Giovanelli was quoted by Sky TG24 as saying that the city had been hit by an "apocalyptic"' storm.

Some city residents used social media to offer shelter to those forced out of their homes.

The BBC Weather Centre says the flooding was caused by a deep area of low pressure that has been sitting over the Mediterranean, bringing sustained heavy rain.

The unstable conditions are expected move across Italy and further east, bringing further downpours and the threat of flooding, particularly in Venice.

The storm caused extensive damage to farms in Sardinia and disrupted a number of flights to and from mainland Italy.

Italian President Giorgio Napolitano has expressed "solidarity with the communities involved" and "heartfelt sympathy to the families of the many victims".

Hundreds of people have been evacuated from their homes

Ships were battered by gale winds and big waves off Cagliari

Flood water gushed down roads and into homes

Rescue workers are looking for a number of people still reported missing