Seven scientists and other experts were sent for trial on manslaughter charges today for failing to warn people of a devastating earthquake that killed more than 300 people in central Italy in 2009.

Defence lawyers condemned the charges, saying it was impossible to predict earthquakes.

Judge Giuseppe Romano Gargarella ordered the members of the national government's Great Risks commission, which evaluates potential for natural disasters, to go on trial in L'Aquila on September 20.

The judge said the defendants "gave inexact, incomplete and contradictory information" about whether smaller tremors felt by L'Aquila residents in the weeks and months before the April 6, 2009 quake should have constituted grounds for a warning.

The 6.3-magnitude quake killed 308 people in and around the medieval town, which was largely reduced to rubble. Thousands of survivors lived in tent camps or temporary housing for months.

Swarms of much smaller tremors had rattled L'Aquila in the months before the quake, causing frightened residents to wonder if they should evacuate.

Defence lawyers contend that since quakes cannot be predicted, the accusations that the scientists and civil protection experts on the commission should have sounded an alarm that a big quake was coming make no sense.

"As we all know, quakes aren't predictable," said Marcello Melandri, lawyer for defendant Enzo Boschi, a scientist who heads the National Institute of Geophysics and Volcanology. In any case, Mr Melandri contended, the panel "never said, 'stay calm, there is no risk."'

Although earthquakes cannot be predicted, experts said after Japan's recent devastating quake that an early warning system in place there to detect the Earth's rumblings before they can be felt helped save countless lives in that country.

In L'Aquila's case, the head of the national civil protection agency had asked the Great Risks commission to evaluate the situation after months of small tremors.

Many of the structures that collapsed in the 2009 quake were not properly built to standards for a quake-prone area like the central Apennine region of Abruzzo. Among the buildings which cracked and crumbled was L'Aquila's hospital, just as it was struggling to treat 1,500 injured.

Nobody inside the hospital, which was built in the 1970s, was killed or injured in the quake.