NEW YORK—Interpublic Group's PR firms delivered high single-digit growth in 2013, aided by a strong fourth quarter of the year.

The group's CMG unit, which includes PR firms Weber Shandwick, GolinHarris and DeVries, grew 7.8% on an organic basis in 2013, reaching $1.3bn in revenue. In the fourth quarter of the year, CMG agencies were up 11.7%.

It is understood that the group's PR firms beat both of those CMG figures, led by the largest PR agency — Weber Shandwick. The firm, said CEO Andy Polansky, delivered particularly strong growth in the US, Brazil and Asia-Pacific.

Europe, admitted Polansky, remained softer, with a strong UK performance offset by difficult market conditions in France, Spain and Italy.

"We believe that we’ve hit bottom in those markets and we’re seeing some encouraging signs but I think it’s too early to say," said Polansky of the 2014 forecast for Continental Europe. "I’m feeling very bullish about the business from the overall perspective. Weber Shandwick continues to take market share and is pushing beyond our traditional peer group in winning business."

In particular, Polansky pointed to social media and digital work as the "primary engine for growth." In an earnings call this morning Interpublic Group CEO Michael Roth singled out CMG agencies, including its PR firms, for strong performances in the US and Asia.