More than 250 people have been killed across Europe as a potentially worsening week-long cold snap shifts west, blanketing large parts of the continent with snow.
Forecasters on Sunday predicted the deep freeze, which has already forced Bosnia to declare a state of emergency and airports to close, will continue.
The death toll included hundreds of homeless people who have frozen to death in what has become the harshest European winter in decades.
Russian gas exporter Gazprom, which supplies fuel to much of Europe, said it would be unable to meet increased European demands and had reduced supplies "for a few days" to ease the crisis in Russia.
Snow fell on Rome's Colosseum for the first time in three decades, disrupting air and rail travel, and Venice's famous canals have frozen over.
About 160,000 people in central and southern Italy were without electricity, and power company Enel said 1,000 workers were trying to fix damaged power lines.
Bodies on the streets
In Ukraine, where at least 122 people have died, the most in Europe, 78 bodies have been found on the streets. Night- time temperatures there have dropped to -33C.
Metro stations in the capital, Kiev, have become sanctuaries of warmth for the homeless.
Emergency authorities have set up hundreds of heated tents around the country to provide food, drink and shelter.
"I live in a social care home most of the time. But they throw you out of there at eight in the morning," said Olexander, a homeless man, at a refuge in a Kiev park on Saturday.
"It is good they have thought of putting these up," he said, nodding at the tent. "If we can just get through this frost, things will get easier."
On Saturday afternoon, Bosnia's capital city, Sarajevo, declared a state of emergency after more than a metre of snow fell.
The state of emergency order said that all schools must stay closed, that women and children should stay home, and that men should only work if necessary.
It also ordered men who own shovels, or vehicles big enough to plough snow, to help the city clear streets, especially those leading to hospitals.
No gas emergency, yet
Amid the freeze, vital Russian gas deliveries were curtailed in nine countries as the cold weather increased the country's domestic demand.
Marlene Holzner, a spokeswoman for European Union Energy Commissioner Guenther Oettinger, said Russia was going through an extremely cold spell and needed more gas to keep its citizens warm.
Russia’s gas contracts "allow for certain flexibility in case they also need the gas. And that is the situation that Russia is facing at the moment," she said.
The European Commission put its gas co-ordination committee on alert on Friday, but it said the situation had not yet reached an emergency level as nations pledged to help each other if needed.
In Serbia's capital, Belgrade, soldiers were deployed to clear the central boulevard.
Hundreds of unemployed people responded to an offer of $13 to join snow clearing efforts.
In the country's mountain villages, thousands of people have been trapped under heavy snow and blizzards
Those stranded are stuck in 6,500 homes in remote areas cut off by icy, snowy roads as banks reached up to five metres.
Relief efforts in the country are concentrated on evacuating the sick, food delivery and fuel distribution.
"We are trying everything to unblock the roads since more snow and blizzards are expected in the coming days," Serbian emergency police official Predrag Maric told the AP news agency.
Emergency crews were pressing hard to try to clear the snow to deliver badly needed supplies. Helicopters were dispatched to some particularly remote areas in Serbia and neighbouring Bosnia.
On Bosnia's Mount Romanija, near Sarajevo, a helicopter landed in the small town of Ozerkovici, where a single nun lives in a Serbian Christian Orthodox monastery surrounded by just a few village residents.
Wrapped tight in a black jacket and a scarf, Sister Justina greeted aid workers at her monastery: "I live alone here," she said, but noted "God will help me."
Deaths have also been reported in Poland, Bulgaria and Romania.