Pictures: And Hel freezes over

Boats at Evia island, northeast of Athens, Greece. Picture / Reuters

Boats are covered with snow in Hel, Poland, as temperatures in Europe fell towards -30C.

Vienna's subway tracks cracked, and German zoos moved penguins indoors as a deadly deep freeze tightened its arctic grip on much of Europe.

The cold has killed more than 50 people in Russia.