Wearing black shirts and badges, traders headed by Confederation of All India Traders National Vice-President A M Vikkramaraja staged demonstrations here.
The traders also laid siege to houses of MPs from the state who supported the government's decision to allow FDI in multi-brand retail, Vikkramaraja said.
December four and five would be observed as "foreign direct investment protest days as the decision will largely affect traders families", he said.
They would intensify their stir if a motion was passed in Parliament on the decision.
"Traders will not accept foreign investments at any cost", he had said earlier.