BELGRADE, Serbia — Freezing temperatures and heavy snowfall have killed at least six people and caused travel chaos across the Balkans, with rescue teams struggling to reach passengers stranded in buses and cars in Serbia on Sunday.

Officials said four people have died in Croatia and two in Serbia as a result of blizzards in the region of southwestern Europe over the weekend, closing airports and roads and blocking public transportation in big cities.

People traveling in vehicles waited for hours on several roads in Serbia’s northern province of Vojvodina, including the main highway leading from Belgrade to the Hungarian border, before rescue teams could free them from 50 centimeters (20 inches) of snow that had fallen in just a few hours.

A woman gave birth to a healthy baby in a stranded truck on her way to a hospital, and named her Snezana, or “Snow White” in Serbian, state TV reported.

By late afternoon, 660 people, including 30 children, were evacuated from stranded vehicles, Serbia’s emergency authorities said, adding that army tanks were used to remove heavy trucks that skidded and blocked highways.

Ivica Dacic, who serves as Serbia’s prime minister and interior minister, ordered all available police personnel to take part in the rescue operations.

The airport in Zagreb, Croatia, was closed for several hours Saturday, and some roads were closed because of high winds and heavy snow. The situation improved in Croatia on Sunday, but a warning against driving remained in place because of icy roads.

Croatian authorities said it was the heaviest snowfall in Zagreb in 57 years.

Authorities in Serbia and Croatia warned people to stay indoors.

Blizzards also hit Slovenia and Bosnia.

As the storms headed east across the Balkans on Sunday, Romania’s army was trying to clear snowbound roads as the country voted in a parliamentary election.