LONDON—WPP's PR firms have sustained their quarterly growth after a prolonged period of decline, according to the group's Q1 trading update today.

The group's PR firms, which include Burson-Marsteller, Hill+Knowlton Strategies, Ogilvy PR and Cohn & Wolfe, grew 1.9% on a like-for-like basis in the first quarter of this year, marking the second consecutive quarter of growth. The improvement comes after the PR revenues declined 1.9% in 2013.

On a constant currency basis, including the effects of acquisitions and disposals, PR revenues grew by 2.9%. WPP CEO Sir Martin Sorrell pointed to expansion in all regions excluding the Middle East and Latin America, noting that growth had been particularly strong in mainland China, the UK, Asia-Pacific and Africa.

The increase took WPP's PR revenues to £212m for the quarter, accounting for 8.2% of total group earnings. On a reported basis, the unit declined by 4.1% during the quarter, due to the currency effects of the strong British pound.

Overall revenues were up 7% on a like-for-like basis to £2.6bn. However, Sorrell reiterated his concern about "known unknowns" — specifically Eurozone fragility; Middle East prospects; a China/BRICS hard landing; and, the US deficit.

Warming to his theme, this time Sorrell also brought up two "unknown unknowns" — "the acceleration of Sino/Japanese tensions over the Diaoyu/Senkaku Islands and, secondly, the crisis in the Ukraine."

"All in all, whilst clients may be more confident than they were in September 2008, they broadly remain unwilling to take further risks," said Sorrell. "They remain focussed on a strategy of adding capacity and brand building in both fast growth geographic and functional markets, like digital and containing or reducing capacity, perhaps with brand building to maintain or increase market share, in the mature, slow growth markets."