A UN spokesperson confirmed that two security staff were injured in the clashes, which is being investigated by Brazilian authorities.
The UN said its staff followed “established protocols” and took protective action.
Hundreds of protesters had earlier marched to the venue in the Amazon city, according to another witness.
Luiz Inácio Lula da Silva, Brazil’s president, has highlighted indigenous communities at this year’s Cop30 as key players in the negotiations.
