Attacks against broadcasting groups, public companies or embassies have been frequent in Greece in recent years, and are usually blamed on anarchist or far-left organisations.
The homemade bomb went off at around 2:30am, 45 minutes after an anonymous telephone warning to another TV network.
Police cordoned off the neighbourhood in the Athens suburb of Neo Phaliro and evacuated the building, which contains the offices of Skai, as well as those of Kathimerini, a centre-right daily critical of the government.
Both are owned by the Alafouzos shipping family.
Police said the bomb was placed in a narrow street near a fence around the building and smashed windows on the facade.
At the time, Skai said in a statement the blast had caused "major damage".
"The terrorist attack will not discourage us," it said, accusing the government of failing to do enough to protect the media despite "recurrent threats against the station".
OLA has previously claimed to be behind at least five other similar blasts, none causing fatalities, since its formation in 2013.
The group last claimed a bombing outside the Athens Court of Appeal in December 2017, which caused extensive material damage.
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