The world's biggest beer festival, the Munich Oktoberfest, has broken with tradition to allow the sale of mulled wine to warm up drinkers during an unusually cold spell.

Organisers permitted the sale of the sweet, warm beverage at the 171st annual Oktoberfest, which has been hit by rain and gale force winds, but they made clear it was an exception.

Eight refreshment stalls have been permitted to sell mulled wine, 1,800 litres of which have been drunk so far, the Munich tourist office said.

That compares with 2.3 million litres of beer sold in the first week of the two week festival.