France's next president Nicolas Sarkozy entered a period of pre-office seclusion Monday, disappearing from view a day after his election triumph, as the country braced for his radical economic reforms.

The 52 year-old president-elect was seen late morning leaving a luxury hotel on the Champs-Elysees accompanied by his wife Cecilia and their son Louis. They were driven off separately in two limousines and press photographers were prevented from following.

Family friends said they had gone on a three day holiday, and would not reveal where.

"He has not had a day off -- including weekends -- in more than five months and he just wants a break," said Francois de la Brosse, who is close to the Sarkozys.

"Here's a guy who's worked his way to the top. All his life he has had a boss. Today he is the top man. I think he deserves three days to reflect on running the world's fifth power," he said.

In an interview last week Sarkozy said that if he won he would go into retreat "in order to immerse myself in the office, take the measure of the heavy responsibilities that will weigh on my shoulders, and rest after the clamour of the campaign."

Sarkozy scored an emphatic 53-47 percent victory Sunday over his Socialist opponent Segolene Royal, winning an unambiguous mandate for his programme of tax cuts, work incentives and curbs to union powers.

For the next ten days Jacques Chirac will remain as president -- officiating Tuesday at ceremonies in Paris marking the end of World War II -- before a hand-over of powers at the Elysee palace on Wednesday May 16.

Leaders from major western powers, including US President George W. Bush and German Chancellor Angela Merkel, were quick to congratulate Sarkozy, who is expected to forge closer ties with Washington and work to raise Europe's global standing.

Franco-American relations cooled in 2003 after Chirac, took a leading role opposing the Iraq war at the United Nations.

British Prime Minister Tony Blair spoke of his "respect" for Sarkozy and stressed the importance of an outward-looking France.

"For countries like ours, it's through alliances with others that we exert influence, between Britain and France, in Europe and of course with the USA," Blair said.

Friends of Sarkozy said the impact of his triumph was only now beginning to sink in.

"We have won a new president but I fear we have lost a friend. When a person becomes president of the Republic, he is elevated above mere personal considerations," said close advisor Patrick Devedjian.

"When the news came in on Sunday, I had the impression that suddenly the whole weight of France fell on his shoulders," he said.

Sarkozy was expected to move fast to enact his reforms. He is banking on a clear majority for his Union for a Popular Movement (UMP) party in legislative elections in June, after which he is to call a special session of the National Assembly to vote through the first stage of his programme.

These include the abolition of tax on overtime, deep cuts in inheritance tax, a law guaranteeing minimum service in transport strikes, and rules to oblige the unemployed to take up offered work.

On the social front he has pledged minimum jail terms for serial offenders and tougher rules to make it harder for immigrants to bring extended families to France.

Before that he has the task of naming a prime minister, with former social affairs minister Francois Fillon and the current employment and social cohesion minister Jean-Louis Borloo named as the most likely candidates.

Tens of thousands of supporters celebrated into the night Sunday in the Place de la Concorde in Paris, where Sarkozy issued a ringing appeal for national unity.

"I want to say to everyone: I will not betray you, I will not lie to you, I will not disappoint you," he said.

Warnings that a Sarkozy victory would trigger large-scale violence in the high-immigration suburbs were not borne out. However there were sporadic outbursts of trouble across the country with some 730 cars burned overnight and nearly 600 people detained.

French newspapers of the left and right agreed that Sarkozy -- often attacked as a divisive figure -- had won a clear mandate for reform.

"With the strong legitimacy his indisputable electoral performance gives him, the new president of the Republic can now begin his great transformation, but taking care, of course, to reconcile the French," wrote the right-wing Le Figaro.

"Nicolas Sarkozy is a legitimate president, elected without rotten tricks or hesitation," wrote the left-wing Liberation. "Tough, but it's the people's will. Thatcher without the petticoats? Let us prepare ourselves..."