BUDAPEST - Hungary deployed tanks to reach thousands of motorists trapped in heavy snow on Friday in a sudden cold snap and high winds which also struck parts of the Balkans, Slovakia and Poland and have left at least four people dead.

Snow stranded people in cars, buses and trains through the night and conspired with strong winds to cut off dozens of towns and villages in Hungary. The situation was critical on the M1 motorway linking Budapest and Vienna where hundreds of cars and trucks got stranded in the snow, most of them for over 20 hours.

A policeman walks at the M1 highway, 80 km west of Budapest, March 15, 2013. Thousands of Hungarian motorists got trapped in heavy snow on the motorways as a sudden cold snap and high winds struck the country. [Photo/Agencies]

By 1730 GMT disaster units had rescued most people stranded in the snow, putting up 12,000 in temporary shelters until the weather improved, Prime Minister Viktor Orban told a news conference.

He said 155 people were still out on the roads waiting for help, including one transplant patient in an ambulance whose life was in danger.

"The situation is particularly difficult and serious on the M1 motorway near the town of Babolna where there is a wall of snow, spanning 12 km (7 miles) with some gaps, and due to the strong winds even the deployment of helicopters is difficult," Orban said on his return from an EU meeting in Brussels.

A Reuters photographer travelling with a rescue convoy said high winds had caused snowdrifts on the motorway up to a metre (3 feet) high, with some cars totally buried.

Two people were killed in an accident on another Hungarian motorway on Thursday when dozens of cars collided. Tens of thousands of people were without power in the northeast of the country.

Government spokesman Andras Giro-Szasz got stranded in snow on a road overnight until a rescuer pulled his car out at 4 am, he told local Inforadio.

Many people took to Facebook to appeal for help.