PARIS—Former French President Nicolas Sarkozy was detained for questioning by magistrates Tuesday as part of an investigation into alleged illegal financing by former Libyan dictator Moammar Gadhafi of his successful 2007 election campaign, a judicial official said.
The investigation centers on millions of euros in payments that investigators suspect Gadhafi may have made to Mr. Sarkozy’s campaign in the years leading up to his victory. The allegations first broke into public view in 2011, days before NATO countries launched a bombing campaign championed by Mr. Sarkozy to support rebels fighting Gadhafi’s government. Gadhafi’s son, Saif, said in a television interview at the time that “Sarkozy must first give back the money he took from Libya to finance his electoral campaign.”
Tuesday’s interrogation marks a crucial step in a multiyear probe that has led investigators hunting for evidence in the rubble left by Libya’s chaotic civil war. Many potential witnesses were either killed or living in countries beyond the reach of French authorities. Investigators had yet to question Mr. Sarkozy, preferring instead to gather evidence that could support the allegations against him.
The allegations against Mr. Sarkozy gained momentum in April 2012, shortly before Mr. Sarkozy lost his re-election campaign to François Hollande. The French website Mediapart reported on a document allegedly drafted by the head of Libya’s intelligence service in December 2006 pledging to provide €50 million ($61.7 million) for Mr. Sarkozy’s campaign. Mr. Sarkozy has said the document is a forgery, but it became a crucial piece evidence in the French investigation.
Investigators have also been examining allegations made by Ziad Takieddine, a businessman and associate of Mr. Sarkozy, that he helped set up payments between Libya and Mr. Sarkozy’s campaign.
For years, the probe has been stymied by two problems: Investigators couldn’t find evidence of whether the payments were made or how the money was potentially used by the Sarkozy campaign. It is unclear if Tuesday’s developments indicate that investigators have made a breakthrough on either front.
In a television interview in 2012, Mr. Sarkozy dismissed as “grotesque” allegations that he received financing from Gadhafi. “If he had financed it I wouldn’t be very thankful,” Mr. Sarkozy said. A lawyer for Mr. Sarkozy couldn’t be reached for comment Tuesday.
In a separate case, Mr. Sarkozy has been ordered to stand trial over allegations he broke campaign financing rules by overspending in his failed re-election bid in 2012. He has denied being aware of any overspending in that campaign.
In 2016, Mr. Sarkozy again sought election, running in the center-right primaries. But he was defeated in the first round of voting.
Write to Matthew Dalton at Matthew.Dalton@wsj.com and William Horobin at William.Horobin@wsj.com