An unknown assailant threw a firebomb at the Athens home of Greece's deputy health minister in a pre-dawn attack Monday that caused minor damage and no injuries, police said.
Authorities detained four people on suspicion of involvement in the 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.
Polaris, a colourful 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.
The governing left-wing Syriza party issued a statement condemning the attack.
"It is clear that neither Syriza nor the government is intimidated and that society stands firm against such practices," it said.