Croatia's Ivo Karlovic broke the fastest serve world record when he fired a 251 kmph (156mph) blast during his country's Davis Cup tie against Germany in Zagreb.

The 2.08m-tall Karlovic, back from Achilles surgery, was partnered by Ivan Dodig and produced the serve in the fourth set of their losing doubles rubber on Saturday against Philipp Petzschner and Christopher Kas.

"The ITF confirmed today that Croatia's Ivo Karlovic broke the world record for the fastest serve," the ITF said in a statement.

Karlovic beat the previous mark of 249.4 kph (155mph) held by American Andy Roddick.

Reuters