Furious farmers opposed to German government plans to cut tax breaks for agriculture used tractors to block roads across the country on Monday in an escalating dispute.

The coordinated nationwide demonstration targeted motorway access ramps in particular, snarling traffic, and followed a smaller ill-tempered demonstration in Berlin last month.

"We are exercising our basic right to inform society and the political class that Germany needs a competitive agricultural sector," German Farmers Association President Joachim Rukwied told Stern magazine.

"That's the only way to ensure the supply of high-quality, homegrown food."

Police reported blockades and major traffic disruptions due to slow-moving tractor convoys from the early morning hours across Germany.

Authorities in the rural northern state of Mecklenburg-Western Pomerania said all of its autobahn ramps were impeded.

Farm equipment blocked the centres of cities including Berlin, Hamburg, Cologne and Bremen, with up to 2,000 tractors registered for each protest.

In the capital, farmers began gathering on Sunday evening at the Brandenburg Gate landmark in the heart of the government quarter.

Farmers have been up in arms over government plans to withdraw certain tax breaks for the agricultural sector this year.

Thousands travelled to Berlin to protest against the move in December, blocking roads with their tractors and dumping manure on the street.

The protests prompted the government to partially walk back the planned subsidy cuts on Thursday.

A discount on vehicle tax for agriculture would remain in place, while a diesel subsidy would be phased out over several years instead of being abolished immediately, the government said.

The agriculture sector however said the move did not go far enough and urged Berlin to completely reverse the plans, which were announced after a shock court ruling forced the government to find savings in the budget for 2024.

Late on Thursday, around 30 agitated protestors targeting the reforms trapped Economy Minister Robert Habeck and other passengers on a ferry, preventing them from disembarking.

The demonstration was widely condemned across the political class for its implicit threat of violence.