Pope Francis has said that a cold he is suffering from will force him to skip a week-long Lenten spiritual retreat with senior Vatican officials south of Rome that had been due to start later today.

The pope made the surprise announcement to thousands of people in St Peter's Square during his first public appearance since last Wednesday, when he was seen coughing and sneezing.

The Vatican has said he is suffering from a "slight indisposition".

"Unfortunately a cold will force me not take part this year (in the retreat). I will follow the meditations from here," the 83-year-old pontiff said after coughing a couple of times during his weekly Sunday appearance from a Vatican window.