The world's largest agricultural fair, Berlin's "Green Week", kicked off Thursday with Greenpeace activists heckling the German agriculture minister, calling for a ban on genetically modified potatoes.

The fair, now in its 75th year, is expected to attract some 400,000 visitors over the next 10 days, as well as 1,600 exhibitors from 56 countries, with Hungary this year's guest of honour.

The two female activists, dressed in traditional Bavarian garb, were escorted out by security personnel before they could unfurl a banner.

The minister, Ilse Aigner, refused to halt her speech and continued through the protest.

The fair opens to the public on Friday and runs until January 24.