Karim Tabbou was one of the most-recognisable faces during unprecedented mass rallies, led by the Hirak pro-democracy movement, that began in February 2019.
One of Algeria's leading opposition figures, Karim Tabbou, has been arrested again, rights groups have said.
He was detained Friday evening at his home, the rights groups said.
Algeria's Human Rights League (LADDH) said on its Facebook page: "We still don't know the reasons for this new arrest.
Tabbou was one of the most-recognisable faces during unprecedented mass rallies, led by the Hirak pro-democracy movement, that began in February 2019. They demanded a sweeping overhaul of the ruling system in place since the North African country's independence from France in 1962.
On Tuesday Tabbou published on his Facebook page a "homage" to another activist, Hakim Debbazi, whose death the Rights League announced. Debbazi had been detained in February.
"Physically dead, the martyrs of the just causes are more than alive," Tabbou wrote.
'Fight for' state of law
He blamed authorities for the death of "modest and humble" Debbazi after a heart attack, and said the activist had been "committed body and soul to the Hirak."
Tabbou called on people to honour Debbazi's "sacrifice" and "continue our fight for the advent of a state of law".
Tabbou leads a small, unregistered opposition party, the Democratic Social Union (UDS).
In March 2020, he was sentenced to one-year in jail for "undermining national security". The conviction stemmed from his criticism of the army's involvement in politics.
He was also detained and released on other occasions, including just before last June's parliamentary election which Hirak boycotted.
The Hirak protests forced longtime president Abdelaziz Bouteflika to step down. Demonstrations continued in a push for deep reforms but the movement waned when the coronavirus pandemic struck.
More than 300 people are detained in Algeria over links to the Hirak or rights activism, the National Committee for the Release of Detainees (CNLD) says.