Pope Francis, announcing that he will issue a new document on the protection of nature, said on Wednesday he was doing so because a "terrible world war" against the environment was taking place.

Speaking at his weekly general audience, Francis said the document would be issued on Oct. 4, the feast day of Francis of Assisi, the patron saint of the environment.

It is a followup to his influential 2015 encyclical - the highest form of papal writing - which spoke of the need to protect the environment, face the dangers and challenges of climate change and reduce the use of fossil fuels.

The pope has said the new writing was meant to bring the 2015 "Laudato Si" (Praised Be) encyclical "up to date with current problems".

Describing nature as a "sacred gift from the creator," the pope urged people to take the side of the "victims of environmental and climatic injustice".

He called for an end to "the senseless war on our common home, it is a terrible world war".

U.S. climate envoy and former secretary of state John Kerry told Reuters in an interview in June after meeting the pope that the 2015 encyclical had a "profound impact" on the climate conference that year which set goals to limit global warming.

In the eight years since Laudato Si was published, the world has seen an increase in extreme weather events such as more intense and prolonged heat waves, more frequent wildfires and more severe hurricanes.

Francis said last month that such events showed that more urgent action was needed to tackle climate change and appealed to world leaders "to do something more concrete to limit polluting emissions".

He said the new document would be an Apostolic Exhortation, another form of papal writing.

After Laudato Si was issued, some conservative Catholics allied with conservative political movements and corporate interests, particularly in the United States, fiercely criticised the pope for backing the opinion of a majority of scientists who say global warming is at least partly due to human activity.