MUNICH, Germany (Reuters) - Thousands of visitors, many of them dressed in traditional lederhosen or dirndl corseted dresses, descended on Munich on Saturday for the start of the annual Oktoberfest, the world’s largest beer festival.

Munich’s mayor, Dieter Reiter, kicked off the festivities by tapping open the first beer keg with a traditional shout of “O zapft is!” (“It’s tapped” in English).

Revelers arrived early to secure spaces at the coveted long communal tables in tents, where visitors swig beer, munch on sausages, pretzel or pork knuckle, and listen to oompah bands.

Oktoberfest has its origins in a horse race that took place in 1810 to celebrate the wedding of Bavarian Crown Prince Ludwig and Princess Therese of Saxony-Hildburghausen.

The public festivities on the Theresienwiese open ground - named after the bride - became more elaborate as time went on, with stalls and amusement rises and it gradually turned into a folk festival.

Oktoberfest attracts around six million visitors every year, with some traveling from abroad for the experience. This year’s festival runs from Sept. 22 to Oct. 7.