Saboteurs have attacked a winery in south-western New South Wales, destroying nearly 500,000 litres of wine.

Police say the offenders entered the business at Yenda, near Griffith, some time last weekend.

They drained 10 tanks holding 490,000 litres of mixed wine, worth more than $800,000.

Police are appealing for public help to identify those responsible and have asked anyone with information to call Crime Stoppers on 1800 333 000.