Vatican City (AFP) - Pope Francis has shrugged off recent in-fighting in the Vatican and other stresses of his job by joking: "I am not on tranquilisers".

"There is corruption in the Vatican. But I am at peace," the pontiff said in a personally revealing interview with Italy's Corriere della Sera, published on Thursday.

In it, the erstwhile Jorge Bergoglio reveals how feelings of anxiety he sometimes experienced while he was bishop of Buenos Aires disappeared following his elevation to the papacy.

And he insists that he is losing no sleep over the manoeuvring of conservatives opposed to his reforms of Church teaching and governance.

The 80-year-old says his secret for dealing with stress is to write down all his problems in letters to Saint Joseph.

He then places the missives under a statue of the man described in the bible as the carpenter father of Jesus.

"And now he is sleeping on a mattress of letters! That's why I sleep well: it is the grace of God. I always sleep six hours. And I pray," Francis said.

Francis's reform drive has run into opposition from conservative cardinals and entrenched interests in the Vatican bureaucracy.

Tensions have appeared to be running particularly high of late.

Francis last month dismissed the head of the Knights of Malta after the ancient order challenged his authority in a dispute seen as being linked to a broader row over the direction of the Church.

And the last week has seen a series of anti-pope posters plastered all over Rome by unidentified agitators.

Asked how he dealt with such tensions and the challenges he faces, Francis quipped: "I'm not on tranquilisers.

"The Italians offer a good lesson - to live in peace you need a healthy 'couldn't care less' attitude.

"I don't mind telling you that what I am going through is a completely new experience for me.

"In Buenos Aires I was more anxious, I admit it. I felt more tense and worried. Basically I wasn't like I am now.

"From the moment I was elected I had a very particular feeling of profound peace. And that has never left me. I am at peace. I don't know how to explain it."

In what may have been an allusion to opponents led by US Cardinal Raymond Burke, Francis implied he had made his intentions clear in meetings with other senior clerics before his election.

"In the general assemblies we discussed the Vatican's problems, we discussed reforms. Everyone wanted them," he said.