Six cars had their tyres slashed while another six had their tyres let down, in the old part of Portimão, along Rua José Buísel.
The vehicles that suffered this act of vandalism were parked on the public street.
A local believes he saw the culprit, but the suspect ran away from the scene.
Portimão PSP police were told of the goings on at around 4.30am and throughout Sunday received various complaints from those targeted.
Authorities are investigating to identify the culprit.