Stefan Markovic slipped and stumbled on Belgrade's icy streets and cursed both the Russians and the Ukrainians for the bad air he's breathing.

"Those damned Soviets!" he shouted. "First they destroyed us with their communism. Now they create more misery. They even poisoned the air we breathe."

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A thick cloak of smog choked the capitals of Serbia, Bosnia and Hungary this week as residents and businesses resorted to burning oil, wood and coal — anything that might help them ward off the midwinter chill amid a natural gas dispute between Russia and Ukraine that has cut off supplies to Europe.

Russia invited EU leaders to an energy summit in Moscow on Saturday, while Ukraine countered with a pre-emptive strike and convened a meeting with European officials on Friday. No head of state has announced plans to attend the Moscow summit. Ukraine doesn't oppose a summit but insists it not be in Moscow.

The dispute is now stretching into its third freezing week and the fallout has been severe: at least a dozen confirmed deaths, hundreds of factory shutdowns that could cost billions in lost productivity — and millions of people left to shiver in unheated homes.

As if trembling in subfreezing apartments wasn't bad enough, a winter storm encased Belgrade in ice. Doctors urged the elderly to stay indoors, warning that their limbs could snap like firewood if they fell.

But bitter cold drove 70-year-old Marija Jovanovic onto the glistening streets.

"I cannot sit at home and shiver," she said. "Walking keeps me warm."

In neighboring Bosnia, Serbia became an unlikely savior by sharing some of its own precious gas supplies.

No one missed the irony: Sarajevo froze during the 1992-95 Bosnian war, when Serb forces laying siege to the city shut off its gas, water and electricity.

A week ago, Boris Tadic, Serbia's Sarajevo-born president, personally intervened and arranged for an emergency gas delivery. But there was a potentially deadly side to the gift. Authorities cautioned that there could be explosions if residents didn't properly re-light heating systems.

Within hours, the first blast dampened Sarajevo's newfound relief. Five members of the Hadrovic family were injured, including 44-year-old Amy Hadrovic, who suffered burns so severe she had to be brought to a clinic in Germany for skin grafts.

Rabija Ljutovic, 72, wasn't taking chances.

"I called the gas company and will wait for their team to come and turn this thing on for me," she said. "No need to blow myself up."

Across eastern Europe, the crisis hit businesses and factories already pinched by the global recession.

At the usually bustling Munja battery factory in Zagreb, Croatia, there was only eerie silence. Machines were turned off earlier this week after Croatian authorities decided they'd better switch off gas to industry and keep people as warm as possible in homes and schools.

"The workers are at home. Where else would they be?" said Ivan Miloloza, the manager, whose factory is losing 2 million kuna ($370,000, 280,000 euros) a day. "There is no production, so we sent them home to wait, to rest."

"We're like a hotel at peak season that has its fridges full of food, but no stove to cook on," he said. "It's worse than during the war."

Bulgaria, the poorest member of the EU, may have suffered the most. Even before the gas stopped flowing, the 27-nation bloc had frozen millions in funds to pressure the ex-communist country to clean up rampant crime and corruption.

Twice this week, angry Bulgarians demonstrated outside parliament in the capital, Sofia. On Wednesday, dozens were injured, including 14 police officers, when demonstrators hurled stones and bottles.

"I want this government to resign because it cannot guarantee my basic needs — a normal salary, a heated home and safety for my family," said Ivan Nenov, a 56-year-old Sofia electrician.

Even in corners of the region where support for Russia runs high, there has been suffering.

In scenes that seemed to come straight out of the Cold War era, bread lines stretched down streets and people in parkas huddled around stone-cold radiators in the ramshackle houses of Moldova's pro-Russia separatist region of Trans-Dniester.

Bread ran out when factories realized there wasn't enough gas to heat the ovens. Residents rushed out to stockpile, buying five or six loaves at a time.

A little heat has started to seep back into their homes, but Elena Gromova, 27, won't soon forget the extra misery the gas outage added to an already difficult life.

"We were freezing cold," said Gromova, who lives in the separatist capital of Tiraspol. "Nobody was sending their children to kindergarten. They were afraid the poor mites would freeze to death there."

Back in Belgrade, Serbs braced for a fresh round of misery.

On Friday, officials warned that large sections of the country might go completely without heat by Jan. 24 if gas doesn't start flowing again.

Markovic, a 31-year-old unemployed engineer, said the Serbian government is partly to blame for failing to store gas reserves and tying itself too closely to Russia.

"What do they want us to do?" he asked. "Freeze to death?"