The Union of Concerned Scientists denounced the watershed ruling, in which the six Italian scientists and a government official were sentenced to six years in jail for multiple manslaughter, as "absurd and dangerous."

It cited an earlier warning by the American Geophysical Union that such litigation would "discourage scientists and officials from advising their government or even working in the field of seismology and seismic risk assessment."

The American Association for the Advancement of Science (AAAS) also condemned the verdict, saying years of research had shown "there is no accepted scientific method for earthquake prediction that can be reliably used to warn citizens of an impending disaster."

"We worry that subjecting scientists to criminal charges for adhering to accepted scientific practices may have a chilling effect on researchers, thereby impeding the free exchange of ideas necessary for progress in science."

Tom Jordan, who chaired an international commission convened after the 2009 L'Aquila earthquake to offer forecasting recommendations, also opposed the verdict, even though the commission's findings were used by the prosecution.

"It's incredible to me that scientists who were just trying to do their jobs have been convicted of manslaughter," said Jordan, a University of Southern California professor who heads the Southern California Earthquake Center.

"The system was flawed, but I'm afraid this verdict is going to cast a pall on anyone trying to make things better."

Jordan said his report, which was submitted to the government before the charges were made, was "used as part of a Monday-morning quarterbacking," an American football metaphor that refers to judging decisions based on hindsight.

The US Geological Survey declined to comment on Monday's verdict, saying: "As a federal science agency, it would be inappropriate for the USGS to comment on the legal proceedings and outcome of the Italian courts."

Under the Italian justice system, the seven remain free until they have exhausted two chances to appeal the verdict.

The 6.3-magnitude earthquake on April 6 killed 309 people and devastated the walled medieval town of L'Aquila.