Publicis' stock surged by as much as 7% after Campaign reported that the group had held talks with a potential private equity investor.

Traders said that had triggered the sharp gains in Publicis' stock.

"There are no talks of any sort going on," a spokeswoman for Publicis told Reuters.

The stock subsequently trimmed gains to 3.5% at 44.3 euros by 1429 GMT.

(Reporting by Julien Ponthus, Thyagaraju Adinarayan and and Pamela Barbaglia; Editing by Mathieu Rosemain and Elaine Hardcastle)