Two home-made explosive devices have been detonated outside the childhood home of Manuel Fraga, the last surviving member of the regime of General Francisco Franco, a Spanish official said.
No-one was injured.
An official from the Interior Ministry office in Lugo province in north-west Spain said the blasts broke windows and damaged the facade of the house, which is being turned into a museum by the conservative Popular Party, which Mr Fraga founded.
The devices were composed of explosive powder of the kind used to make fireworks and butane gas canisters used for camping stoves.
The official said there was no immediate claim of responsibility.
Mr Fraga is 88 and has a seat in the Senate.