ATHENS, GREECE -- A severe snowstorm disrupted road and air traffic Monday in the Greek capital of Athens and in neighboring Turkey's largest city of Istanbul, while snow blanketed most of Turkey and Greece, including several Aegean islands.

The Greek government declared a holiday Tuesday in the greater Athens area, parts of central Greece and the islands to keep people from leaving home. Key branches of the civil service as well as food stores, gas stations and pharmacies will stay open.

“We ask citizens to avoid leaving their homes. It will be a difficult night,†Climate Change and Civil Protection Minister Christos Stylianides said. “The height of the snow is unprecedented in some areas.â€

The storm snarled traffic in Athens and put most public transport out of action. Army and fire service teams were deployed late Monday to extract hundreds of motorists trapped for hours in snowed-in cars, taking them to rented hotel rooms. Some people abandoned their vehicles and walked home in the snow.

Rail transport was also affected, and state ERT TV reported that three people were lightly injured when an engine accidentally crashed into a stuck train with about 200 people on board that it had been sent to extract. The accident occurred near the town of Livadia in central Greece.

Turkish authorities in Istanbul, a metropolis of 16 million people, suspended intercity bus service and temporarily blocked travel to the city from Turkey's Thrace region. People stranded on roads abandoned vehicles to walk home or crowded subway and other public transportation. Schools across Turkey are closed for a winter break, but universities halted classes for two days. Public offices and shopping malls closed early.

The Istanbul governor's office announced that civil servants would be allowed to stay at home Tuesday, except for those employed in security, health and transportation sectors.

“It is a difficult night,†Istanbul Mayor Ekrem Imamoglu declared. He urged people not to leave their homes. Snow had reached 80-85 centimeters (31-33 inches) deep in some parts of Istanbul, he said.

Flights in and out of Istanbul Airport were suspended until 4 a.m. Tuesday. Authorities worked to clear runways and a road leading to the airport, where the roof of a facility used by Turkish Airlines' cargo department collapsed from the weight of snow. No one was hurt.

Flurries were forecast to continue over the next few days in Istanbul and Greece.

In Greece, schools in many areas were closed. Government spokesman Giannis Oikonomou said more than 46,000 school classes were being held online.

The snow came down thick and fast throughout the day in central Athens, settling on the marble temples of the ancient Acropolis.

Snow chains were mandatory for cars on many roads, while trucks were banned from the main highway heading north from Athens. Nevertheless, the icy conditions and lack of snow chains on some vehicles left some drivers reported being stuck in their cars for more than five hours on the Greek capital's roads.

Power cuts occurred in parts of Athens and nearby areas as well as the island of Evia in the evening, knocking out heating systems.

Several domestic and international flights to Athens airport were canceled, while subway service to the airport was partially suspended. COVID-19 vaccination centers in the wider Athens region and Evia were closed Monday and would remain closed Tuesday.

Snow is common in the Greek mountains and in northern Greece but is less frequent in central Athens and on Aegean islands. Last year, a major snowstorm caused severe problems in the capital, knocking out power for days. Thousands of trees collapsed from the weight of the snow and ice.

In neighboring Albania on Monday, all elementary and high schools closed for three days because of cold weather. Authorities advised people to avoid driving as temperatures reached -17 C (about 1 F) in eastern Albania.

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Associated Press writers Llazar Semini in Tirana, Albania, and Suzan Fraser in Ankara, Turkey, contributed to this report.