The search was part of an investigation into an allegedly fake job given to his wife. He denies any wrongdoing.

Mr Fillon has vowed to continue his presidential campaign, despite growing pressure for him to step down.

He was once seen as the favourite to win the election but his poll ratings have dropped since the scandal emerged.

The allegations circling around the Fillon family focus mainly on his Welsh-born wife Penelope, who is also reported to be facing an investigation.

The Le Canard Enchaine newspaper alleges she was paid €831,400 (£710,000; $900,000) over several years for working as a parliamentary assistant for Mr Fillon and his successor, but had no parliamentary pass - raising questions over whether she did the work she was paid for.

The raid on Thursday morning happened as the candidate visited winegrowers in southern France. His parliamentary office had already been searched last month.

Many on the right will see the operation as another sign of how the scandal has totally eclipsed Mr Fillon's ability to run a campaign, the BBC's Hugh Schofield in Paris reports.

For the first time since the affair broke out a month ago, there is open dissension in the ranks about his candidacy, our correspondent adds.

Senior Republicans have gathered support for ex-Prime Minister Alain Juppe, 71, who was defeated by Mr Fillon in the primaries.

On Thursday evening, thousands of supporters turned out to his rally in the town of Nimes. "You have a fighter before you," Mr Fillon told a cheering crowd. "I have no intention of giving in."

Much of the scandal has centred on Mr Fillon's wife, Penelope

On Wednesday, Mr Fillon said he had been summoned to appear before a judge over the case.

He complained he was the victim of a "political assassination", and vowed to continue his run for president - despite previously pledging to stand down if his case was placed under formal investigation.

Following his announcement, several key allies resigned, including his foreign affairs spokesman and deputy campaign director.

Mr Fillon will appear in court on 15 March, just two days before the deadline for candidates to submit their final applications.

The first round of the election takes place on 23 April, followed by a run-off on 7 May.