Police had been hunting the pair since the end of last week and they were arrested a few minutes apart in the southeastern port city, the police source said.
"Mahiedine M. and Clement B., both French nationals, both well known for their radicalisation by the specialised services and classified on the terror watch list since 2016 and 2015, met each other in prison where they shared their cell for about two months in 2015 for common crimes", said Molins.
A search of a rented apartment was continuing.
Two Frenchmen arrested in Marseille on Tuesday planned an "imminent and violent attack" ahead of the first round of the presidential election on Sunday, France's interior minister said.
Macron and conservative candidate Francois Fillon have pledged more robust counterterrorism efforts, but remain committed to Europe's open borders.
Fillon was also shown a photo of the two suspects, the newspaper reported.
French presidential candidate Emmanuel Macron (center), poses for a selfie with employees of the meat pavilion at the Rungis wholesale food market south of Paris, April 18, 2017.
Christophe Sanz, a supporter of French centrist presidential candidate Emmanuel Macron, glues a campaign poster next to a poster of far-right candidate Marine le Pen, in Bayonne, southwestern France, Wednesday, April 19, 2017.
Rouhani says Iran needs "no one's permission" to build missiles
The Islamic Republic says its military power poses no threat to other countries and is merely based on the doctrine of deterrence. However, Ahmadinejad said Wednesday that the Supreme Leader never barred him from rerunning for the presidency.
Le Pen, who, according to polls conducted in the past week is likely to move onto the second round, has argued that France must quit the euro, and has advocated a referendum on European Union membership, similar to the one that led to Brexit previous year.
In the last days of campaigning all bets are off in the French presidential election.
The outcome is likely a second round run off that would pit Le Pen, Macron, Melenchon or Fillon against one another in a number of combinations.
Until now, Le Pen has struggled to get her opponents in the presidential race to debate her party's trademark tough security and immigration stance.
"We have never seen a four-way contest like this in the first round of a presidential election", Frederic Dabi of the Ifop polling institute told AFP. "We are not afraid", he told the crowd.
He said at this stage investigators have not determined "the day, the targets and the exact circumstances" of a potential attack.
With the country still under a state of emergency, Fekl said more than 50,000 police, gendarmes and soldiers would be deployed for each leg of the election.
Le Pen also said she would issue an order to freeze long-term visas for a two-week period so the government can verify, among other things, that the recipients aren't taking jobs away from French citizens.