The Greater Chattogram Public Transport Owners and Workers Unity Council called an emergency meeting amid the protests
Chittagong Metropolitan Magistrate Court on Monday turned down a police plea for their five-day remand.
Nasir Mohammad, 45, and his brother-in-law Salahuddin, 22, were arrested on Sunday from the city.
Mohammad, a shopkeeper by profession, threatened to bomb the court on Oct 14 disguising himself as a member of banned outfit Jaamat'ul Mujaheedin Bangladesh (JMB).
Police say they had not found Mohammad's militant links and that he had made the threat 'out of desperation'.
Mohammad claimed he had issued the threat to get a verdict in a land dispute case in his favour.