"They have found a small tumor in one of my lungs and that's why I came here to the INEN," he told the local N news channel, referring to a medical institute which specializes in cancer treatment.

"Happily, the tumor markers are normal," the 79-year-old said after hearing that its size presented no major danger.

But he must return to the hospital every four months for monitoring.

Over the past year, Fujimori has become a frequent hospital visitor and was pardoned in December by then president Pedro Pablo Kuczynski on grounds of his failing health, in a decision which divided the country.

As well as suffering from cardiac issues and high blood pressure, Fujimori has also undergone several operations for a carcinogenic growth on his tongue.

The former president, who also holds Japanese citizenship, was first jailed in 2007 and convicted in 2009 for his role in a series of killings by a death squad which was targeting alleged members of the Shining Path guerrilla group in the 1990s.

He has also been convicted of embezzlement and bribery.