Four people have died across Serbia in the relentless snow storm that along with frigid temperatures has snarled traffic, closed schools and led to power outages in the country, local media reported on Tuesday.

Hardest hit by the snow storm is the northern province of Vojvodina, in which four people have died in weather-related incidents and where most of 60 Serbian schools closed due to the snowfall, Radio Television Serbia said.

Although the main international transit route running the length of Serbia remains slow but passable, a section near the Bulgarian border was closed for more than five hours due to an overturned transport truck.

With the exception of trucks carrying food stuffs, all other heavy vehicles have been ordered off main roads by Serbian police. Traffic on many regional roads has been restricted to passenger vehicles with full winter equipment.

Over the weekend, some travelers were stranded for up to 22 hours on roads before they could be reached by emergency crews.

Predrag Maric, head of emergency situations, offered his apology for the "hell" endured by stranded passengers, explaining that a convoy of 30 transport trucks had blocked the highway and only eight snow removal vehicles were available to deal with the heavy snowfall.

Belgrade Mayor Dragan Dilas also apologized to citizens for the shortage of city transit vehicles on the roads over the past days. Homeless in the Belgrade shelter slept in hallways, as there were insufficient beds to meet the demand.

Prime Minister Ivica Dacic threatened to dismiss emergency and transportation workers who failed to help with snow removal activities.

Drifting snow has cut off many isolated mountain villages in the southwest of the country, many without electricity.

The central district of the city of Nis was without heating with the breakdown of the municipal heating plant.