By William Horobin

PARIS -- Former French President Nicolas Sarkozy appeared at risk of being knocked out of the first round of a key primary, early vote counting showed, potentially marking a significant upset in the race to become France's next president.

The results from 2,913 of the 10,228 polling stations across the country on Sunday showed Mr. Sarkozy winning only 24.4% vote after centering his campaign on pledges for hard-line security measures and a clampdown on immigration.

Mr. Sarkozy was hobbled by a late surge in support for his former prime minister, François Fillon, who ran in the conservative primary race on a platform of delivering a shock to the French economy with deep spending cuts and labor overhauls. Mr. Fillon won 42.8% of the early votes, ahead of the 26% received by Bordeaux Mayor Alain Juppé, who recent polls showed had been the favorite to win the primary.

The breakdown of the vote could still change significantly as more results come in Sunday evening. The initial vote isn't a projection and is heavily based on counts from the smallest towns around the country.

If the full count Sunday confirms that Mr. Fillon and Mr. Juppé are in the lead, they will advance to a runoff next Sunday.

The elimination of Mr. Sarkozy in the first round would upend a conservative primary that is set to have sweeping consequences in France. Polls show the winner would be best placed to win the presidential election in May against the National Front's Marine Le Pen.

Until last week, polls had shown Mr. Sarkozy would easily reach the second round and go head-to-head with Mr. Juppé in a second-round race centered on questions of French identity and security in the aftermath of a string of terror attacks in France.

(END) Dow Jones Newswires

November 20, 2016 16:03 ET (21:03 GMT)

Copyright (c) 2016 Dow Jones & Company, Inc.