The Vatican has denied an Italian media report that Pope Francis has a benign brain tumor.

"The circulation of entirely unfounded news regarding the health of the Holy Father by an Italian newspaper is gravely irresponsible and unworthy of attention," chief Vatican spokesman Father Federico Lombardi said in a statement.

"Furthermore, as is clearly evident, the pope is carrying out his very intense activity in a totally normal way," he said.

Francis later held his weekly general audience before tens of thousands of people in St. Peter's Square and was due to return to a three-week gathering of Roman Catholic bishops from around the world, which he has been attending daily.

The newspaper Quotidiano Nazionale, a national paper based in central Italy, reported on its front page on Wednesday that the 78-year-old pope had secretly flown by helicopter to a small Tuscan town "some time ago" to see a Japanese doctor.

The paper reported that the Argentine pontiff was diagnosed with "a small dark spot on the brain", but that it was curable.

The pope has appeared to be in good health in recent months apart from some leg pain due to the fact that he suffers from sciatica, for which he undergoes regular physical therapy in the Vatican.