The activists of Bangladesh Jamaat-e-Islami and its student wing Islami Chhatra Shibir brought out a sudden procession in the capital's Karwan Bazaar area on Wednesday afternoon.
The law enforcers had to fire around six blank shots to disperse the Jamaat-Shibir men, said Enamul Haque, officer-in-charge of Kalabagan Police Station.
Around 150 demonstrators brought out the procession chanting slogans in favour of their Thursday's hartal.
Jamaat called a countrywide dawn-to-dusk hartal for Thursday demanding immediate release of opposition leaders including war crimes suspects and restoration of the caretaker government system.
During the demonstration, the Jamaat-Shibir men also demanded cancellation of the international crimes tribunals that were designed to deal with the trial of the war crimes suspects.
Police dispersed the Jamaat-Shibir men when they were marching through the Panthapath-Greenroad intersection, said the Kalabagan