A surge in demand following a heatwave has led Italian electricity firms to order the first country-wide power cuts for more than 20 years.
Temperatures have been high for the past weeks
Soaring temperatures have led people to switch their air conditioners, fans and refrigerators on to full power.
The jump in demand has stretched the country's national grid to breaking point and utility firms cut power for up to one and half hours in major cities on Thursday.
The operator of Italy's national grid, GRTN, blamed the cuts on an unexpected cut in power imports from France.
Italy cannot meet all of its domestic power needs from its own power stations, and imports several thousand megawatts from other countries every day.
It normally imports 2,650 megawatts from France daily, but late on Wednesday the GRTN was told the power imports would be cut by 800 megawatts.
Italy's own power production has also been hit by the heatwave, with hydroelectric plants reducing output because of the lack of water.
The result was a wave of power cuts across the country - the first since 1981.
The blackouts trapped people in lifts and traffic lights were switched off.
Italy's Industry Minister Antonio Marzano called on Italians to cut back their use of energy.
"Our emergency plan has five levels. Right now we are only at level one," he said.
"What happens over the coming days depends entirely on the heat."
GRTN has already said that there is a risk of further power cuts on Friday.