The guards must swear an oath of allegiance to the Pope

Pope Benedict has honoured the Swiss Guards, the small army that protects the Vatican, at a mass inside St Peter's Basilica in Rome.

The Guards are celebrating their 500th anniversary this weekend, and the Pope thanked them for their five centuries of service.

They first came to Rome as Swiss mercenaries in 1506 to serve under Pope Julius II, known as the "warrior pope".

As on 6 May every year, a group of new recruits are being sworn in.

It marks the date when 147 Swiss Guards died in 1527, protecting Pope Clement VII during the Sack of Rome.

"To be a Swiss Guard means to adhere without reservation to Christ and the Church and be ready to offer your life for this," Pope Benedict said in his homily.

"I express a deserved and deeply felt thank you and I call on you to carry on with courage and loyalty."

There was applause as dozens of the Swiss Guards, in their striped gold and blue uniforms and carrying their traditional weapon, the halberd, marched away at the end of the mass.

The guards have served a total of 42 different popes and have sworn an oath of allegiance that they will protect the Pope's life with theirs, if necessary.

Each recruit must be Catholic, between the ages of 19 and 30 and must have completed mandatory Swiss military service.