Activists demanded that the organisation and the governments took urgent measures to save the environment, the United Nations Children’s Fund (UNICEF) press service stated.
The complaint targeted Germany, France, Turkey, Argentina and Brazil, which according to Thunberg, are not doing enough to stop global warming.
"Change needs to happen now if we are to avoid the worst consequences. The climate crisis is not just the weather. It means also, lack of food and lack of water, places that are unliveable and refugees because of it. It is scary," Thunberg said at a press conference following her speech before the United Nations, as quoted by the UNICEF statement.
The complaint focuses on a so-called optional protocol, a mechanism that allows children or adults on their behalf to appeal directly to the United Nations to file a complaint to the Committee on the Rights of the Child if they feel their rights are being denied.
"Thirty years ago, world leaders made a historic commitment to the world’s children by adopting the Convention on the Rights of the Child. Today, the world’s children are holding the world accountable to that commitment. We fully support children exercising their rights and taking a stand. Climate change will impact every single one of them. It’s no wonder they are uniting to fight back," UNICEF Deputy Executive Director Charlotte Petri Gornitzka said.
US President Donald Trump said that the young activist has a bright future in response to her powerful speech at the UN General Assembly.
"She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!" Trump wrote on Twitter.
Last week, over four million people in 161 countries took part in Global Climate Strike across the world ahead of the UN Climate Action Summit 2019, inspired by Thunberg.
The strike comes after children from Fridays For Future movement walked out of schools in May to demand action against global warming, asking adults to join them the next time.
Fridays For Future started in 2018 following the call by Thunberg, who protested against the lack of climate action in front of the Swedish parliament every day for three weeks during school hours.