"We are deeply concerned about the protracted crisis in Haiti, and its impact on the ability of Haitians to access their basic rights to healthcare, food, education, and other needs", the UN's Office of the High Commissioner for Human Rights (OHCHR) said in a statement.
It referred to reports that 19 of the deaths were caused by government forces, whereas the other protesters were killed by unidentified armed individuals.
According to the UN statement, at least one journalist was killed and nine others have been injured, with the freedom of the press being seriously jeopardised.
In September, Haitian Senator Jean Marie Ralph Fethiere fired at protesters located near the parliament building, claiming that his actions were an act of self-defence.
As one of the world's poorest nations, Haiti has been struggling with political instability and recovering from the 2010 earthquake which left 300,000 people dead.
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