Prosecutors said the case had been referred to the judicial police in the French capital, six days after Mr Sarkozy tied the knot with the Italian-born former supermodel turned singer-songwriter.

In a posting on Wednesday headlined The obsession with Cecilia, the nouvelobs.com website - run by the left-leaning Nouvel Observateur magazine - said Mr Sarkozy had written to Cecilia eight days before marrying Ms Bruni.

'If you come back, I'll call it all off,' he was reported to have told his ex-wife Cecilia Ciganer-Albeniz.

Mr Sarkozy, 53, remarried less than four months after ending his stormy 11-year marriage to Cecilia, 50, with whom he has a young son, Louis. The couple announced their divorce on Oct 18.

The French president has filed suit against the website for 'falsification, use of false documents and possession of stolen goods', his lawyer Thierry Herzog said on Thursday.

'To my knowledge, it is the first time that a serving president has lodged a complaint against a media outlet,' said Mr Herzog, 'but it is also the first time that a serving president has been treated so badly.'

Under French law, the maximum penalty in such a case is three years in prison and a fine of 45,000 euros (S$92,000). The courts could also order that the source of the story be revealed. -- AFP