The head of Italy's top disaster body quit in protest Tuesday after seven of its members were sentenced to jail over a deadly earthquake in a shock ruling that the global science community warned dealt a dangerous blow to scientific freedom.

Luciano Maiami, the head of the Major Risks Committee, and several top scientists resigned after seven of the body's members were found guilty on Monday of manslaughter for underestimating the devastating L'Aquila quake which killed 309 people in 2009.

Maiami, one of Italy's top physicists and a former head of top particle physics laboratory Cern in Geneva, described the verdict as "a big mistake" and said he had resigned because "there aren't the conditions to work serenely".

The verdict has provoked deep anger and concern in the global science community, with top experts warning of the repercussions and saying their colleagues had been used as scapegoats.

The seven defendants are appealing the ruling by the court in the medieval town of L'Aquila in central Italy. Under the Italian justice system, they remain free until they have exhausted two avenues of appeal.

"These are professionals who spoke in good faith and were by no means motivated by personal interests, they had always said that it is not possible to predict an earthquake," Maiami told the Corriere della Sera newspaper.

"It is impossible to produce serious, professional and disinterested advice under this mad judicial and media pressure. This sort of thing doesn't happen anywhere else in the world," he said.

"This is the end of scientists giving consultations to the state."

All seven defendants were members of the Major Risks Committee which met in L'Aquila on March 31, 2009 -- six days before the 6.3-magnitude quake devastated the region, killing 309 people and leaving thousands homeless.

One of the seven, Mauro Dolce, resigned as head of the Civil Protection's seismic risk office on Tuesday, and the rest of the committee were preparing to follow suit, according to Maiami.

Committee member Roberto Vinci from the National Research Council said he had resigned "to show support for those who, perhaps having reacted with a certain naivety and certainly under great pressure, have been accused of manslaughter".

Michael Halpern of the US-based Union of Concerned Scientists said that without the right to speak freely, they would be vulnerable to scapegoating and persecution.

"Scientists need to be able to share what they know -- and admit what they do not know -- without the fear of being held criminally responsible should their predictions not hold up," he said in a blog.

The appeal hearings are due to take place in the final months of 2013, according to Marcello Melandri, lawyer for Enzo Bosci, the head of Italy's national geophysics institute (INGV) at the time of the quake.

"We will wait to read the grounds for the verdict and then the defence lawyers will work on the appeal, hoping for a better outcome," he said.

"I am still incredulous," he said of judge Marco Belli's decision to give the scientists an even harsher sentence than the four years called for by the prosecutor.

The defendants were also ordered to pay more than nine million euros (almost $12 million) in damages to survivors.

In L'Aquila and the surrounding towns, where rubble from crumbled houses and churches still lies in vast piles in off-limit zones, survivors and families of those killed said they were shocked by the reaction.

"There has not been any trial against science," said Anna Bonomi, spokeswoman for the 3and32 survivors' group which has campaigned for justice.

"If anything, there has been a trial against a system of power," she said, referring to the widely-held belief that the government had conjured up a media-friendly reassuring message to calm skittish citizens before the quake.

"They may convince Italians (that the trial was unfair) but they will not convince us residents: they played with people's lives," she said.

Maiami said that rather than blaming the scientists, prosecutors should be going after the architects and builders who put up poorly built apartments.

It is "deeply wrong that there is no investigation into who constructed houses in a seismic zone in such an inadequate fashion," he said.

Geophysicist Dario Albarello, who heads a project into short-term quake forecasts for the INGV, said "it is not earthquakes that kill, it's badly built buildings that collapse," and described the trial as "a witch hunt."

The government committee met in 2009 after a series of small tremors in the preceding weeks had sown panic among local inhabitants -- particularly after a resident began making worrying unofficial earthquake predictions.

Italy's top seismologists were called in to evaluate and the-then deputy director of the Civil Protection agency Bernardo De Bernardinis gave press interviews saying the seismic activity in L'Aquila posed "no danger".

He advised local residents to relax with a glass of wine.

About 120,000 people were affected by the quake, which destroyed the city's historic centre and medieval churches as well as surrounding villages.

In May this year, northeast Italy was hit by two earthquakes which devastated churches, buildings and factories, leaving 25 people dead and over 15,000 people homeless.