Pope Benedict XVI said last night that bone fragments found inside the tomb of St Paul in Rome had been carbon dated for the first time, "confirming the unanimous and uncontested tradition that they are the mortal remains of the Apostle Paul".

He said that archaeologists had inserted a probe into the white marble sarcophagus under the Basilica of St Paul's Outside the Walls which has been revered for centuries as the tomb of St Paul.

The pontiff said: "Small fragments of bone were carbon dated by experts who knew nothing about their provenance and results showed they were from someone who lived between the 1st and 2nd century. This seems to confirm the unanimous and uncontested tradition that these are the mortal remains of Paul the Apostle."

The Pope, who said the discovery "fills our souls with great emotion", made the unexpected announcement during Vespers at St Paul's Basilica last night, marking the end of the Pauline year held in honour of the apostle. He said that as well as bone fragments, archaeologists had found grains of red incense, a piece of purple linen with gold sequins and a blue fabric with linen filaments in the tomb.

Cardinal Andrea Cordero Lanza di Montezemolo, the archpriest of St Paul's, said that he had known for more than a year that the tests had shown that the bones were those of a man of the 1st century, but had been sworn to secrecy because it had been "up to the Holy Father to make this public". He said this was why the Vatican press office had denied last week that the bones had been identified. "Only the Pope can make such an important and solemn announcement," he said.

The cardinal said he was now waiting for permission from the Pope to open the tomb, which would be a "long and delicate operation" in order to avoid any "structural damage" to the sarcophagus. Andrea Tornielli, the papal biographer, said that Pope Benedict's announcement recalled Pope Paul VI's declaration 41 years ago that the bones of St Peter had been identified.

At the weekend L'Osservatore Romano, the Vatican newspaper, announced the discovery of a fresco in a 4th-century Christian catacomb depicting St Paul. Archaeologists believe it is the oldest known icon of the apostle.

St Paul is believed to have been beheaded in Rome in the 1st century during Nero's persecution of Christians.Tradition holds that fragments of his skull are in kept in St John Lateran but that his other remains are inside the sarcophagus at St Paul's.

The two and a half metre long tomb is buried under layers of mortar and plaster beneath the main altar at St Paul's Basilica and covered by an iron grate. It survived the disastrous 19th-century fire which destroyed much of the building, but is hidden from view. Vatican archaeologists began to unearth it in 2002 after many pilgrims to Rome during the 2000 Holy Jubilee year expressed disappointment at not being able to visit or touch it.

The Pope marked the feast day of Saints Peter and Paul today by bestowing palliums on recently appointed archbishops, including Monsignor Vincent Nichols, the new Archbishop of Westminster. The pallium, a band of white lambs wool decorated with black crosses, is symbol of an archbishop's pastoral role as shepherd of his flock and of the authority he derives from the pontiff.