Nicolas Sarkozy was detained for questioning today (1 July) in a widening corruption probe, a judicial source told AFP, in an unprecedented move against a former French president.
Anti-corruption investigators can hold Sarkozy for questioning for up to 24 hours, with a possible extension of another day.
Sarkozy had turned himself in for questioning a day after investigators detained his lawyer Thierry Herzog and two magistrates.
The investigators are seeking to establish if the former president, with the help of Herzog, attempted to pervert the course of justice.
They suspect Sarkozy, 59, sought to obtain inside information from one of the magistrates about the progress of another probe, and that he was tipped off that his mobile phone had been tapped by judges looking into the alleged financing of his 2007 election campaign by former Libyan dictator Muammar Gaddafi.
The case could be devastating for Sarkozy's hopes of a political comeback in time for the next presidential campaign in 2017.
On 6 May 2012, the French investigative website Mediapart said it had uncovered a document from Libya's former secret services showing that Gaddafi's government had decided to finance Sarkozy's run at the presidency when he was interior minister.
>> Read: French campaign takes nasty turn
Sarkozy, whose government had played a key role in the ouster of Gaddafi, has repeatedly denied receiving any money from the former Libyan leader, who was captured and killed by fighters from the Libyan National Liberation Army in 2011.
In Brussels, Sarkozy is remembered for exerting a duopoly over the European Union with German Chancellor Angela Merkel - a tandem dubbed 'Merkozy'. Together, the pair oversaw much of the measures adopted during the euro zone's sovereign debt crisis and appeared as the driving force behind EU decision-making. Both hail from the same centre-right political camp.
Since the election of the socialist François Hollande as French President, the Franco-German relationship has been strained due to the ideological differences between the two leaders.