The Brihamumbai Municipal Corporation administration has sealed offices of all political parties at the BMC headquarters here following a face-off between the rival Shiv Sena factions. Municipal Commissioner Iqbal Singh Chahal, who is also the BMC's administrator, told Press Trust of India on Thursday that the civic body took the step on Mumbai Police's instructions after the incident on Wednesday at the civic headquarters, which has offices of all major political parties on the ground floor of the heritage building.