Publicis saw demand for advertising rebound in October to achieve more than 7 percent organic growth in group sales, reversing a September slump with strength in the U.S., emerging markets and digital ads.

"While October numbers are extremely good, we should remain cautious: the fourth quarter is always uncertain particularly December," said Chief Executive Maurice Levy in an emailed statement.

"At this point in time, we cannot yet confirm that growth and confidence are back."

September's contraction depressed Publicis' monthly revenue by 1.6 percent compared with a year earlier and led it to post weaker than expected third-quarter sales.

(Reporting by Leila Abboud and Gwenaelle Barzic)