Brazilian President Jair Bolsonaro said Monday he had been diagnosed with a kidney stone and would undergo surgery in September to remove it.

The far-right leader, 65, has had a series of health issues, including four surgeries stemming from an attack in which he was stabbed in the abdomen during his 2018 presidential campaign.

"I felt a little pain, so I went for a checkup. But I'm fine. It's an age thing," Bolsonaro told CNN Brasil.

He said doctors had performed an ultrasound and told him the kidney stone was slightly larger than a bean.

The president's office did not immediately respond to a request for further details.

Bolsonaro is also coming off a bout with Covid-19 that put him in quarantine for nearly three weeks in July.

The president, who has repeatedly downplayed the coronavirus pandemic, said his infection was never serious, thanks to his "athletic past" and his course of treatment with hydroxychloroquine.

He has controversially pushed the anti-malaria medication as a wonder drug for Covid-19, despite studies showing it is ineffective against the disease.

That has earned him criticism in Brazil, which has the second-highest number of infections and deaths in the pandemic, after the United States: more than 3.9 million and 121,000, respectively.

Bolsonaro was stabbed in the stomach by a suspected radical leftist during a campaign rally in September 2018, just over a month before he was elected president.

The attack forced him to undergo four operations on his stomach, the most recent in September 2019.

In March, he said he needed to undergo a fifth operation related to the incident, which he said "should be the last."