Fiat rose around 19% in early session trading in Milan, while Renault's shares were up 16%.

"Strong fits in product/scale, further indications that OEM consolidation is on the agenda, an opportunity to re-deploy capital at Renault, and confirmation of FCA as an M&A target, are positives," wrote brokerage Jefferies.

Fiat's advisers on the deal include Goldman Sachs, Nomura and boutique investment bank d'Angelin & Co.

(Reporting by Sudip Kar-Gupta; Editing by Bate Felix)