A woman walks in a snowstorm in Skopje, Macedonia January 10, 2017. REUTERS/Ognen Teofilovski

BELGRADE/SARAJEVO (Reuters) - At least eight people have died as subzero cold and heavy snow enveloped the Balkans, with tens of thousands stranded in remote regions or left without heating in temperatures that dipped as low as -20 degrees Celsius.

Central and east-southeastern Europe have been gripped by a mid-winter deep freeze and snowstorms for days. With temperatures dropping below -30 Celsius, at least 25 people died over the weekend, mainly in Poland.

In the Balkans, a father and son died from frigid cold in Serbia, state RTS TV reported on Tuesday. A man fell into a well and survived 52 hours in extreme cold before being found by neighbours, local officials said.

Thousands of people were trapped in outlying central and southern regions of Serbia by heavy snow. A state of emergency was declared in 11 municipalities.

Serbian authorities also halted navigation along the Danube river after it iced up along some stretches. Bulgaria and Hungary also banned shipping along their sections of the Danube because of dangerous floating ice.

In neighbouring Bosnia, three people in remote parts of the country froze to death while nearly 50,000 in the central town of Zenica lost their home heating due to a malfunction in a boiler at the ArcelorMittal steel mill, which provides thermal power to households.

Three men in their 50s froze to death in Albania, and municipal authorities took several hundred homeless people to heated shelters.

In Turkey, one person died and 10 people were injured when a snow-laden canopy collapsed at a mosque in Istanbul.

In northern Greece, temperatures plummeted to freezing levels not seen since the 1960s, while Athens’ ancient monuments, such as the Parthenon temple on the Acropolis rising above the city, wore a rare mantle of snow.