Monegasques and tourists are preparing for a day of festivities

The move follows the death of his father, Prince Rainier, in April. The Grimaldi family has ruled the statelet for some 700 years.

The mayor will later symbolically hand over the town's keys to the prince. Fireworks and a ball will follow.

A more formal ceremony is to be held in November with foreign heads of states.

Illegitimate son

Tuesday's ceremonies have been overshadowed by the latest revelations to rock the Riviera royal dynasty.

In an interview on French television on Monday, Prince Albert, 47, discussed his illegitimate baby son, Alexandre.

He also suggested that other paternity suits were a possibility.

Profile: Prince Albert

Until recently the tall, balding Albert was the least scandal-prone member of the family, unlike his sisters Princess Caroline and Princess Stephanie, says the BBC's Caroline Wyatt in Paris.

He was a bachelor who kept his private life private despite rumours of liaisons with models and actresses.

Then a French air hostess originally from Togo revealed in Paris Match magazine that Albert was the father of her 22-month-old son, Alexandre, and published photos of Albert with the baby.

In Monday's interview, Prince Albert said he was shocked at the way Alexandre's existence had been revealed.

His illegitimate son will not be able to inherit the throne, although Prince Albert has acknowledged paternity and assumed his financial responsibilities.