RIO DE JANEIRO — President Jair Bolsonaro of Brazil on Friday fired the head of a government agency that had revealed a big increase in deforestation in the Amazon, with the dismissal inciting protests from environmental organizations and public workers.

The sacking of Ricardo Magnus Osório Galvão, a well-respected physicist, came a day after Mr. Bolsonaro angrily claimed that people within the government were damaging the country’s image abroad by disclosing the rate at which the world’s largest tropical rain forest is withering.

Mr. Bolsonaro and his minister of the environment, Ricardo Salles, on Thursday had held a news conference during which they cast doubt on his own government’s figures, which are routinely released monthly, that showed a steep rise in deforestation in the Amazon this year.

[Read our article on protections for the Amazon being slashed.]

“The numbers, as I understand it, were released with the objective of harming the name of Brazil and its government,” Mr. Bolsonaro told reporters, speaking alongside Mr. Salles.