Belgium has handed over to France two men believed to have helped a key suspect in last year's Paris attacks flee to Brussels, Belgian federal prosecutors said.

Mohamed Amri and Ali Oulkadi are suspected of helping Salah Abdeslam in the crucial hours after the 13 November massacre, which left 130 dead and hundreds wounded.

The pair allegedly worked with Hamza Attou, who has already been extradited.

"Within the framework of the Paris attacks of November 2015, Mohammed A and Ali O have been surrendered to the French authorities today," a statement said, referring to the men only by their initials.

Amri and Attou are suspected of accompanying Abdeslam back to Brussels, getting him past three police checks in France before crossing the border into Belgium.

Oulkadi is thought to have then driven Abdeslam across Brussels on 14 November, the last place the top suspect was traced before his capture in the Belgian capital four months later.

Abdeslam, the only surviving member of the ten-man jihadist team that attacked Paris, was extradited to France in April.

Attou told Belgian investigators that Abdeslam called him and Amri late on 13 November to ask them to come for him "because he had had an accident," according to a source close to the case.

He claimed that they did not know of Abdeslam's involvement in the attacks until after they joined him in Paris.

The source quoted Attou as recounting that Abdeslam said he was "the sole survivor of these attacks" and that "they would pay for my brother's death".

Abdeslam's brother Brahim blew himself up outside a Paris cafe during the attacks.

Once in Brussels, Attou said he took Abdeslam to a market to buy new clothes and to get a haircut before taking him to Oulkadi, who showed him to a safe house in the city's Schaerbeek area.

Amri and Attou were arrested on 14 November in Brussels' Molenbeek district, where Abdeslam grew up, and charged in Belgium.

Belgium agreed to extradite Attou to France earlier this month but on condition that he serve any jail time in Belgium.