According to the Times, Francis also suggested cloistered nuns should spend half an hour talking to people, "because the cloistered nun needs this human rapport".
"The smiles of nuns open up the heart, he said. "This week it's your turn to spend half an hour giving something to eat to the poor who ask for a sandwich. This week it's your turn to smile at the needy. Don't forget this. You must always leave time to listen to people," said Francis.
"Even in the hours of contemplation, of silence. Some monasteries have an answering machine and people call to ask for prayers for one thing or another, — think link with the world is important."
Even cloistered nuns needed to spend "half an hour chatting" to people, he said, "Because the cloistered nun needs this human rapport. This is very important," he added.
Francis however said he did not want nuns spending all their time away from their prayers, and cited one cloistered nun who was constantly outside her convent with the poor. "This, he said, "is a mistake."
In 2012 Francis warned a gathering of nuns against turning into "old maids", telling them to be more motherly, "like the figures of Mary and the Mother Church."
However, earlier this year he lent his support to American nuns, who had been placed under investigation by the Vatican for spending too much time campaigning on social justice issues and too little time battling abortion.
In April, the probe was unexpectedly dropped, following a decision by Francis.
