File photo.

Turkish authorities detained an opposition Istanbul district mayor and five others on Wednesday over alleged irregularities involving building and occupancy permits, broadcaster NTV reported.

The detention of Uskudar Mayor Sinem Dedetas marks the latest development in an unprecedented legal crackdown targeting municipalities run by the main opposition party, which has challenged President Tayyip Erdogan’s ruling party.

Those detained included Dedetas, the district deputy mayor, the municipal secretary, an architect, a business agent and a contractor, NTV reported.

Police carried out simultaneous raids at 11 addresses across Istanbul and seized digital materials from the suspects, the broadcaster said.