Shouting angrily, the protesters demanded access to the UN compound where thousands of delegates from countries around the world are attending this year's UN climate summit in Belem, Brazil.
Some waved flags with slogans calling for land rights or carried signs saying "our land is not for sale."
An Indigenous leader from the Tupinamba community near the lower reaches of the Tapajos River in Brazil told Reuters that they were upset about ongoing development in the forest.
"We can't eat money," said Gilmar, who uses only one name.
"We want our lands free from agribusiness, oil exploration, illegal miners and illegal loggers."
Security guards pushed the protesters back and used tables to barricade the entrance. A Reuters witness saw one security guard being rushed away in a wheelchair while clutching his stomach.
Another guard with a fresh cut above his eye told Reuters he had been hit in the head by a heavy drumstick thrown from the crowd. Security confiscated several batons.
The protesters dispersed shortly after the clash. They had been in a group of hundreds who marched to the venue.
Security guards later allowed delegates to exit the venue, having earlier asked them to move back inside until the area was clear.
The UN climate agency did not immediately reply to a request for comment. Within the compound, the United Nations is responsible for security.
Brazil's President Luiz Inácio Lula da Silva has highlighted Indigenous communities as key players in this year's COP30 negotiations.
Earlier this week, dozens of Indigenous leaders arrived by boat to participate in the talks and demand more say in how forests are managed.
In a separate interview on Tuesday, a prominent Indigenous leader told Reuters that many from the Indigenous communities were upset with ongoing industry and development projects in the forest. Raoni Metuktire, also known as Chief Raoni, urged Brazil to empower native peoples to preserve the Amazon.
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