Slovak wine makers have finished harvesting frozen Blaufrankisch and Welschriesling grapes that will be used for production of ice wine, trade organisation said on Sunday.

"The wave of frosty weather came suddenly. We had to call people back from their holidays," said Milos Sevcik, production director of Vinarske Zavody Topolcianky winemaking company.

He added that they finished the harvest on New Year's Eve, at temperatures of below -12 degrees Celsius.

Apart from Slovakia, ice wine from Topolcianky has also found markets in Japan, China, and Singapore.

"Demand on these markets is really huge. The locals like the sweet ice wine, but they don't have proper conditions for making it themselves," pointed out Sevcik.

Ice wine is a type of dessert wine produced from grapes that have been frozen while still on the vine. When grapes are collected at year-end, wine will be ready in June at the earliest.