Protesters target Ford headquarters
Cologne city police spokesman Karlo Kreitz said about 100 of the protesters were taken into temporary custody after three officers suffered minor injuries in the fracas.
Police say the protesters arrived on buses from Belgium and blocked the entrance to the plant.
Then a group of 20 to 40 stormed the building and threw stones through windows while others burned tyres and set off fireworks.
Ford has announced plans to shut an assembly plant in Genk, Belgium, jeopardising some 5,000 jobs, and union representatives are currently meeting with company management in Cologne.