Pope Francis led a religious ceremony at the Vatican today, his first public appearance since concerns for his health were raised when he abruptly cancelled a visit to a Rome hospital two days ago.

The 77-year-old pope appeared to be in good health as he presided at a two-hour-long Mass in St. Peter's Basilica on the day the Catholic Church celebrates the feast of Saints Peter and Paul.

Last Friday, he cancelled a visit to patients at Rome's Gemelli hospital minutes before it was to have started because of what the Vatican called a "sudden indisposition".

In his homily, Francis said bishops should not seek gratification by cultivating "those who wield worldly power" but to find their personal security in their vocation to help the poor.

He also gave 24 recently appointed archbishops a vestment known as a pallium, a small circular band worn around the neck which symbolises their unity with the pope.

After the Mass, he made his traditional noon appearance to crowds gathered in St. Peter Square and appealed for dialogue to end the conflict in Iraq.