Vatican City, Holy See — Pope Francis has suspended the use of an oxygen mask, the Vatican said on Wednesday, adding that the 88-year-old's clinical condition was "improving" after more than one month in hospital.

The Argentine pope has been in Rome's Gemelli hospital since 14 February suffering from pneumonia in both lungs, but the Vatican has reported recent progress after earlier worries that his life could be at risk.

"The Holy Father's clinical conditions are confirmed to be improving," wrote the Vatican in a medical bulletin.

He has "suspended non-invasive mechanical ventilation and also reduced the need for high-flow oxygen therapy", it said, adding that there was progress in the pope's motor and respiratory physiotherapy.

The press office later cautioned, however, that suspension of the oxygen mask did not mean it could not be reintroduced further down the line, and added that Francis's discharge from hospital was "not imminent".

Francis's pneumonia has not been "eliminated", but was "under control", it said.  

At the weekend, the Vatican said the Jesuit still required therapies to be administered from the hospital.

After a series of breathing attacks earlier in the pope's hospital stay, his breathing has improved over the past week, with the Vatican on Monday saying he was spending short moments breathing on his own. 

During the day he has relied on a cannula -- a plastic tube tucked into his nostrils -- to deliver high-flow oxygen, which doctors are now reducing. 

Until this week, Francis had worn an oxygen mask, but on Tuesday the Vatican said he had managed without one for the first time.

In a sign of the progress the pope has made over the past week, the Vatican's press office said the next medical bulletin would likely not come before Monday. 

For most of the pope's hospital stay, including critical stages, the Vatican was publishing daily bulletins on the health of Francis, who had part of one lung removed as a young man.

The pope's illness and long spell in hospital has raised questions over who might lead the busy schedule of religious events leading up to Easter, the holiest period in the Christian calendar. 

The Vatican's press office on Wednesday said that no definite decisions had been taken yet in that regard.