Tens of thousands of Argentines marched through the rain in front of the presidential palace on Sunday to demand answers in the case of a young protester who went missing two months ago.
Opposition and human rights groups believe state security forces took Santiago Maldonado, a 28-year-old craftsman, and allege President Mauricio Macri's government is covering up information on his whereabouts.
Maldonado was last seen during an Aug. 1 operation by the National Gendarmerie to end a land occupation in Chubut province by the indigenous Mapuche.
"My intuition tells me the Gendarmerie have him. Where, I don't know," Maldonado's brother, Sergio Maldonado, told reporters at the rally in downtown Buenos Aires.
Protesters marched carrying images of Maldonado's bearded face and signs that read "may he appear alive now."
Potential cases of abuse by security forces are sensitive in Argentina, where the 1976-1983 military dictatorship secretly detained, tortured and killed people in clandestine prisons. Rights groups say up to 30,000 people were "disappeared."
Macri's government has said that there is no evidence that shows security forces detained Maldonado.