In prokaryotes, which process of transcription is catalysed by RNA polymerase only?

RNA polymerase only catalyses the elongation process of transcription. The initiation of transcription is done by sigma ($\mathrm{\sigma }$) unit. The termination of the transcription is acheived by rho ($\mathrm{\rho }$) factor. These two structures are not a part of RNA polymerase. Thus, RNA polymerase can perform the function of elongation only.