Pope Francis has called in his Christmas message for nations to share Covid-19 vaccines, saying walls of nationalism could not be built to stop a pandemic that knows no borders.

In a sign of the times, the Pontiff delivered his traditional "Urbi et Orbi" (to the city and the world) message virtually from a lectern inside the Vatican instead of from the central balcony of St. Peter's Basilica before tens of thousands.

The pandemic and its social and economic effects dominated the message, in which he called for global unity and help for nations suffering from conflicts and humanitarian crises.

"At this moment in history, marked by the ecological crisis and grave economic and social imbalances only worsened by the coronavirus pandemic, it is all the more important for us to acknowledge one another as brothers and sisters," he said.

Stressing that health is an international issue, he appeared to criticise so-called "vaccine nationalism", which UN officials fear will worsen the pandemic if poor nations receive the vaccine last.

"May the Son of God renew in political and government leaders a spirit of international cooperation, starting with health care, so that all will be ensured access to vaccines and treatment. In the face of a challenge that knows no borders, we cannot erect walls. All of us are in the same boat," he said.

Italians are under a nationwide lockdown for much of the Christmas and New Year holiday period. The restrictions mean people are not be able to go to St Peter's Square or the basilica for papal events, all of which have been moved indoors.

Pope Francis also called for peace and reconciliation in Syria, Yemen, Libya, Nagorno-Karabakh, South Sudan, Nigeria and Cameroon and Iraq, which he is due to visit in early March.

He also asked to comfort those suffering from humanitarian crises or natural disasters in Burkina Fasso, Mali, Niger, the Philippines and Vietnam.