PISTOIA, Italy (AP) _ Government warnings that a dangerous earthquake might strike soon sent 100,000 people fleeing in panic from mountain villages in central Italy, authorities said today.

The unprecedented warning by the Civil Defense Ministry followed a moderate quake on Wednesday and was prompted by the region's seismic history. A second, stronger tremor occurred today.

Traffic police said most villagers drove away Wednesday night, taking few personal belongings, after the state radio and television network broadcast repeated warnings in the evening.

The state of alert was called in eight Tuscan villages in the Apennine mountains north of Pistoia and in six villages of neighboring Modena provinceand was to last until Friday morning. But an official of the Civil Defense Ministry said the period of immediate danger appeared to have passed.

The army was mobilized in Bologna, Modena and Florence for possible immediate intervention, including transport of campers and tents.

Officials of the ministry and geologists said that on the basis of previous occurrences in the quake-prone area there was a great risk of a dangerous and destructive quake 48 hours after initial, light tremors.

The experts said the potential epicenter would be in an area about 30 miles south of Modena and 10 miles north of this ancient Tuscan town.

Authorities in Bologna, Modena and Florence made available schools and hotels to shelter those who left their homes. Schools in the danger area have been closed for at least two days.

Local authorities reported that many residents of towns outside the danger area slept in their cars.

Many areas of Italy are prone to quakes and at least four destructive jolts have struck densely populated regions in southern, central and northern Italy since 1974.

''We hope that the warning turns out not to have been necessary,'' Calvino Gasparini, an official of the geophysics institute said Thuesday. ''The seismic history of the Garfagnana area made the alert necessary, however.''