2:01pm UK, Wednesday July 13, 2005

Prince Albert II of Monaco has officially become the new ruler of the French principality.

Day-long festivities opened with a mass at the cathedral where his father Prince Rainier III was buried three months ago.

180 Prince Albert II of Monaco key of city

Prince Albert II of Monaco receives the 'Key of the City'

Albert, his sisters Princess Caroline and Princess Stephanie, and the rest of Grimaldi family attended the event with the archbishop of Monaco, Monsignor Bernard Barsi.

His accession followed Albert admitting on Sundayhe was the father of a flight attendant's child.

The 47-year-old bachelor prince is the only son of Prince Rainier and actress Grace Kelly, who gave up Hollywood to become a princess.

Rainier, who ruled the tiny Riviera principality for more than 50 years, died on April 6.

Albert was automatically given royal powers but his accession, a two-step event, formally places him on the throne.

A further ceremony being planned for November is expected to draw heads of state.

Onlooker Christine Rousguisto, 79, said: "I remember Albert's birth. We've seen him grow up.

"Of course, he's ready for this. He has everything to be a wonderful prince."

The princes of Monaco do not wear crowns but Albert sat on a royal throne during the mass.

The solemn ceremonies were due to end with fireworks and a festive ball under the stars.