Thousands of tractors slowed down traffic in Hamburg on Thursday as farmers converged on a conference of German environmental ministers and senators in the city.

The politicians are gathering to discuss environmental policies, including on insecticides and the protection of groundwater.

Many farmers say the policies affecting agriculture are too impractical and removed from the realities of farming.

They are calling for more engagement with them from politicians and greater influence in decision-making.

Police said 4,000 tractors were heading to Hamburg and warned of traffic delays.