BERLIN — Pan-European media giant RTL Group saw net profit drop more than 15% in the first half of the year, due largely to an increasingly difficult advertising market across much of the continent.

RTL posted net earnings of €274 million ($344 million) between January and June, down from $407 million in the same period last year. First-half revenue climbed 3.3% to $3.5 billion.

In a joint statement, co-CEOs Anke Schaeferkordt and Guillaume de Posch said, “Following an overall stable first quarter, advertising market conditions across Europe became more challenging. Nevertheless, RTL Group has once again generated solid results, thanks to its international scope and diversified revenue streams.”

RTL’s German TV operations kicked in higher profits but that was offset by the difficult market conditions elsewhere, higher investment in programming and a dramatically lower profit by FremantleMedia, the group’s London-based production and licensing unit. Its performance reflected pressure from broadcasters on volumes and margins, and the fact that several productions are not due until the second half of the year.

The company has continued to expand: FremantleMedia Enterprises and Random House, which is also owned by RTL parent Bertelsmann, have pacted to develop scripted TV programming for the U.S. and international markets, based on the publisher’s titles; it finalized plans to launch its first joint venture channel in India, BIG-RTL Thrill, a Hindi-language net targeting young viewers with action-oriented content; and bowed the free-TV RTL Nitro web in Germany, targeting male viewers. In September, RTL will launch its third digital pay TV channel in the Netherlands.

Looking forward, Schaeferkordt and de Posch said they could not speculate on ad market growth. However, they expect a solid performance in the second half, but not at 2011’s record level.