Nothing was moving fast on Sunday

An accident on a power supply line in neighbouring Switzerland caused a domino effect, which triggered grid failure across Italy in a matter of seconds.

At least three people are reported to have died in accidents during the blackout, and power was only restored gradually during Sunday.

Some train services are still disrupted, and there were warnings that 5% of households could still face power cuts on Monday.

Only the island of Sardinia escaped the outage, which struck at about 0330 (0130GMT) on Sunday morning.

It was the latest in a series of major blackouts to affect national power grids - north-east United States and Canada were hit last month, and Denmark and southern Sweden on Tuesday.

High imports

The power failure has highlighted Italy's dependence on energy imports.

The power failure raises serious questions for Italy's national grid

A spokesman for Enel, the Italian utility company, said the country imports up to 17% of its power, compared with a Europe-wide average of 2%.

Power generation is reduced overnight, making Italy more vulnerable to any disruption in supplies from neighbouring France and Switzerland.

A Swiss power company said the problem began when a tree touched a 380,000 volt transmission line near the town of Brunnen at 0300 (0100GMT).

Atel, a Swiss power supply company, said that two French transmission lines also failed shortly afterwards.

"After that, all connections to Italy dropped out," said an Atel spokesman.

He said that poor organisation in the Italian grid, GRTN, made the problem worse.

Environmental opposition to building new power plants means that Italy has become more and more dependant on power imports.

Industry Minister Antonio Marzano called for a backing for a bill to increase power output by 12,000mW, a quarter of the current capacity.

The head of the power company echoed his call.

"I would like my fellow citizens to know that we must build new plants and networks on our territory or the situation will remain the same," said Enel chief executive Paolo Scaroni.

White night in the dark

In Rome, the power cut struck as thousands of people celebrated the city's first "White Night" - an extravaganza of street events.

Four hours no telephone - no television and no public lighting. No police service into street of the city - no public awareness Giuseppe Michieli, Italy Read more of your views

The failure halted the free underground service provided by the city, and left passengers stranded in underground trains.

Heavy rain had already stopped a number of attractions.

The lights also failed inside the Vatican, and emergency generators were started up to provide power to amplify Pope John Paul II's announcement of a list of new cardinals.

Two elderly women died in separate incidents when they fell downstairs in the dark, and a third woman died of burns after a candle set her clothes ablaze.