The police stepped up security deployment in Madhyamgram, Doharia and adjoining localities after BJP supporters staged protests, demanding the immediate arrest of the assailants.

"We are keeping strict vigil in sensitive pockets, and additional forces have been deployed. People should not pay heed to rumours. We appeal to people to maintain peace," a senior West Bengal Police officer told PTI.

Adhikari's close aide Chandranath Rath was shot dead in North 24 Parganas district on Wednesday night in what the BJP described as a "targeted assassination", triggering outrage, protests and fresh allegations of political violence.

According to preliminary information, Rath was intercepted near Doltala in Madhyamgram around 10.30 pm by motorcycle-borne assailants who tailed his vehicle, forced it to stop and opened fire before fleeing.

"We want the arrest of killers. Rath, travelling in a vehicle linked to the leader of the opposition, was shot dead. This is nothing but a planned murder. People are frightened," a local BJP worker said.