BUENOS AIRES, Argentina (AP) — Tens of thousands of Argentines demonstrated in cities across the country Friday holding photos a missing activist who was last seen when border police evicted a group of indigenous Mapuche from lands in Patagonia owned by Italian clothing company Benetton.

The march marked the one-month anniversary of Santiago Maldonado's disappearance. Demonstrators gathered at the Plaza de Mayo square in front of the presidential palace in Buenos Aires asking their government find the 28-year-old alive.

Maldonado's disappearance has hit a raw nerve in Argentina, where human rights groups estimate that about 30,000 people died or were forcibly disappeared during the 1976-1983 military dictatorship.

Maldonado's family says border police detained him when he and others were blocking a road in Chubut province, in the southern region of Patagonia. The protesters were demanding the release of a jailed Mapuche leader wanted by Chile.

Authorities deny any wrongdoing.