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Beer-drinking revellers in colourful costumes are celebrating the start of a week-long street carnival in Cologne, Germany.

Thousands celebrate the start of street carnival in Cologne on Thursday, which marks a non-stop party between Fat Thursday and Ash Wednesday.

Cologne is one of three German carnival strongholds besides Dusseldorf and Mainz, and the celebrations are considered a countdown to the carnival season's pinnacle, Rose Monday.

Women dressed in costumes for "Weiberfastnacht" (Women's Carnival) celebrate in front of Cologne's Cathedral February 27, 2014. (Ina Fassbender/Reuters photo)

Cologne Carnival is celebrated in Germany's predominantly Catholic west and south, with much swaying to traditional ballads and brass bands.

Petra Maddauss, dressed in a costume with blue feathers and a bright blue wig, says this year's celebrations are once again "wonderful".

"It couldn't be any more beautiful. The sun is out and we just hope it stays that way. We are having a great party with lots of swaying and I hope it will last all day!"

Christina Feret, who has opted for a tiger costume and had her face painted, says everything is "perfect".

Women dressed in costumes for "Weiberfastnacht" (Women's Carnival) celebrate in Cologne February 27, 2014.(Ina Fassbender/Reuters photo)

Revellers chant an expression believed to originate from "Koelle alaaf", meaning "Cologne rules".

Carnival has various origins, stemming from the Roman tradition of celebrating the onset of spring. It's also based in ancient Germanic fertility rites, which were later adopted by Christians to usher in the fasting period before Easter.