Former French president Nicolas Sarkozy has formally announced he will run for office again in next year's election.

In an extract of a book released on his Facebook page today, Mr Sarkozy wrote: "I have decided to be a candidate to the 2017 presidential election."

He added: "I've felt I had the force to wage this battle at a so tormented time of history."

Mr Sarkozy, 61, is expected to lead a campaign based on hard-line ideas on immigration and security in a country marked by recent terror attacks.

He must first win the primaries organised by the French right in November where he will face competition from former prime minister Alain Juppe, favourite in the polls.

Mr Sarkozy lost the presidential election to Francois Hollande in 2012 after his first term.

When he left the Elysee Palace, Mr Sarkozy said he was leaving politics and would find a different way to serve his country.

Yet he made a successful comeback in 2014, winning the leadership of the conservative party, known at the time as the UMP.

He explained he was moved to return to politics by the "hopelessness, anger and lack of future" that he sensed among the French. Since then the party changed its name to "the Republicans".

Since 2010, Mr Sarkozy's name has been mentioned in several legal cases relating to corruption and influence-peddling, but he has never been convicted of wrongdoing or faced trial.

The French presidential election will take place next year in two rounds in April and May.

Mr Hollande has not said if he will run for re-election.

Marine Le Pen, the leader of the far-right National Front, has already announced her candidacy.

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