A powerful bomb placed in a bus parked in a depot in Madurai was on Friday defused by police who said it could have been placed to cause disturbance before the next month's local body elections in Tamil Nadu.

Police said the bomb did not work because the wires had not been properly connected.

But it was powerful enough to have caused extensive damage, they said, adding a petrol bunk was also located in the premises of the depot.

Assistant Commissioner of Police Velladurai said the bomb was a sophisticated one with unsophisticated wiring.