Thousands of protesters, backed by a procession of farm tractors, marched in Berlin Saturday for environmental protection and against the industrial agriculture lobby.

Police put the number of demonstrators at over 12,000, while organisers said 35,000 turned out.

While the "Grune Woche" international agricultural fair was taking place in the German capital, the protesters took aim at government policy which prioritised large-scale farming, deemed damaging to health and the environment, to the detriment of small farmers and bio-growers.

"This protest... shows that the desire for a different agricultural policy is now undeniable," said Green party co-leader Robert Habeck, who took part in Saturday's demonstration.

Conservative Agriculture Minister Julia Kloeckner has received "an unequivocal message" from the street, said Saskia Richartz, spokeswoman for the protest organisers.

"We can't feed the whole world if we reduce industrial agricultural production," the agriculture minister responded, while admitting that the sector needs to be "more efficient and respectful of the environment".

Protesting farmers file past Brandenburg Gate. The message at the front reads: 'We are fed up with consumption without conscience' / © AFP

More than 100 organisations took part in Saturday's colourful march, with 171 tractors descending on Berlin from several parts of the country.

The ministerial quarter around Brandenburg Gate remained partially blocked for several hours before the protest broke up peacefully.