Porto coach Sergio Conceicao's family car was "savagely" attacked after this week's Champions League hammering by Club Brugge, the Portuguese side said on Wednesday.
According to local media the vehicle, carrying Conceicao's wife and two sons was targeted following Tuesday's 4-0 defeat.
Supporters threw stones and insulted the trio but they were not injured during the incident.
"Porto totally repudiate the attack on coach Sergio Conceicao's family car, last night, outside the Estadio do Dragao," the two-time European Cup winners said.
"Porto also regret the lack of protection from the authorities, and calls for the author or authors of this savage act to be quickly identified and held accountable," they added.
Conceicao's side remain winless in Europe this season and are third in the Primeira Liga, three points behind leaders Benfica.
The 47-year-old was appointed boss in 2017 and has won eight trophies.
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