"Two plainclothes officers showed up at Lazhari Labter's house at 6:30 pm with a summons, the contents of which I am unaware of," Amine Labter wrote on Facebook late Sunday.
He added that he did not know which of Algeria's security services was holding the 70-year-old, who played a role in the North African country's 2019 Hirak protests, which unseated longtime president Abdelaziz Bouteflika.
The writer's son later said his father would be spending the night at a central police station in the capital.
Labter, a prolific journalist, editor and poet, is known for penning the so-called "18 commandments" of the 2019 protests, urging peaceful demonstrations against the authorities.
The author, who has worked for the International Federation of Journalists, is a former president of Algeria's editors' union and was a founding member of the national journalists' syndicate.
Reporters Without Borders ranks the North African country 134th out of 180 in its 2022 World Press Freedom Index.