For the first time since his hospitalisation around three weeks ago, Pope Francis is showing a good response to treatment, a Vatican source told CNN.

This follows a statement from the Vatican press office on Saturday that described “a good response to therapy” and a “gradual, slight improvement” since his episodes of acute respiratory failure on Monday.

The Vatican source said that this improvement was due to the “gas exchange” in the lungs and the oxygenation of the blood.

However, the risk remains of another breathing crisis remains and the prognosis is still reserved, the source emphasised.

The pope continues to alternate between high flow oxygen therapy during the day and non-invasive ventilation at night, the Vatican press office said.

On Saturday morning, Francis prayed inside a chapel. In the afternoon, he rested and engaged in work activities, the office said, adding that Sunday’s Angelus prayer will again be released in written form.

Starting on Sunday, the pope will participate in the traditional “spiritual exercises” for Lent from the hospital, the Vatican source told CNN.

Since Monday’s incident, the pope has remained in stable condition and received respiratory and motor physiotherapy.

He released a pre-recorded audio message on Thursday thanking his supporters for their prayers.

Uncertainty has continued to swirl in the Vatican throughout Francis’ extended hospital stay.