Congressman Elias Vaz said he had been informed through a freedom of information request that President Jair Bolsonaro's government had approved an order of 35,000 of the erectile-dysfunction pills for the armed forces.

"Our hospitals don't have enough medication, and Bolsonaro and his crew are using public money to buy 'the little blue pill,'" said the opposition lawmaker, calling the purchase "immoral."

The documents he received do not mention Viagra by name, but say the order was for sildenafil, the active ingredient in the drug, said the center-left deputy.

The defense ministry said in a statement the pills were in fact "to treat patients with pulmonary arterial hypertension," or high blood pressure in the lungs, another use for sildenafil.

That did little to stem social media users' mirth.

Cartoons featuring tanks with drooping cannon proliferated on Twitter, where Viagra was one of Brazil's top trending topics.

"This explains why the military's support for Bolsonaro just rises and rises," quipped one user, playing on the far-right president's tight relationship with the armed forces.

Bolsonaro, a former army captain, has packed his administration with members of the armed forces, and is openly nostalgic for Brazil's 1964-1985 military dictatorship, despite its record of rights violations.

"Some say these pills are to help the armed forces f*** democracy even harder," wrote satirical news site Sensacionalista.

Left-wing Congressmen Marcelo Freixo and Elias Vaz meanwhile said they would ask prosecutors to investigate whether something else was swollen about the purchase: the bill.

They said there was evidence the government was overbilled by up to 143 percent -- often a sign of corruption.