Usually, groups of mourners march in the streets and mourn by chanting and reciting religious poems and beating their chests commemorating the martyrdom of Imam Hussain in the Karbala incident. This tradition had existed among the Arabs and later on took the present form in which chest-beating is accompanied by and in harmony with special laments. The mourning Shiite bands of Tehran usually move on the streets carrying pressurized paraffin lamps, special flags, and torches and lament by beat their chests in rhythm with mourning poems.