Demonstrators in the Argentine capital, Buenos Aires, marched on Friday to the Plaza de Mayo square in front of the presidential palace to demand the government disclose information on the whereabouts of 28-year-old Santiago Maldonado, who disappeared a month ago.

"We want a serious and impartial investigation to investigate all the police personnel who were involved," the brother of the missing man asked the crowd, being interrupted by demonstrators with shouts of "murderers, murderers."

Several attacks during the rallies were reported against police headquarters, both in the capital and in the town of El Bolson, in the southern region of Patagonia, where Molotov cocktails were thrown at police headquarters.

Indigenous activist and singer Ruben Patagonia called on the government to "put a brake on all the violence and repression" against his community. He told Spanish news agency EFE that the police had "trampled on very spiritual places."

Soccer star Diego Maradona and Oscar-winning composer Gustavo Santaolalla have joined human rights activists in a social media campaign under the slogan: "Where is Santiago Maldonado?"

Maldonado's family said they believe border police detained him when he and others were blocking a road on August 1 in Chubut province, in Patagonia.

Authorities have denied wrongdoing. A report published by local media and written by local prosecutor Silvina Avila said there was no proof that border police were involved in the disappearance.

Benetton versus Mapuche

On August 1, protesters were demanding the release of Facundo Jones Huala, an imprisoned Mapuche leader wanted by Chile.

The lands belong to Compania de Tierras Sud Argentino, a wool-producing company owned by Benetton, while the Mapuches claim the lands as their ancestral territory.

Raking up old memories

The case has become problematic for the government of President Mauricio Macri with human rights groups accusing it of being part of a cover up.

"We've gone back in time 40 years. I can't accept it," said Rosa de Roisinblit, vice president of the Grandmothers of Plaza de Mayo human rights groups.

"I can't believe that this is happening in a constitutional, democratically elected government," she said.

The Inter-American Commission on Human Rights has urged Argentina to find the missing man.

jbh/sms (AP, EFE)