Greek police say an unknown assailant threw a firebomb at the Athens home of the country's deputy health minister in a pre-dawn attack that caused minor damage and no injuries.

Authorities detained four people on suspicion of involvement in Monday's attack outside the home of Pavlos Polakis. Three of them were later released, while one remained in custody for a separate issue, as he was found to be in the country illegally and was awaiting deportation.

Polakis, a colorful figure who has often sparked controversy, issued an enraged response on social media, accusing the "shadow state" of being behind the attack and saying it was because he had helped uncover political scandals in Greece.