Thousands of people in their nightclothes rushed screaming into the streets tonight as the strongest earthquake in three years shook mainland Italy from the Adriatic to the Mediterranean.

Police said a series of tremors, which struck in waves just before midnight, caused panic in urban areas including Rome, Florence, Naples and Perugia. First reports said five persons were killed.

Damage did not appear to be serious, although the tremors broke gas pipes and sent scaffolding tumbling into the streets.

In the city of Rieti, parts of a medieval wall collapsed and people fled the town in their cars.

The worst-hit area was around Norcia -- a midieval town of 7,000 in the Umbrian region, the hilly heart of Italy.

In Rome and the Vatican, walls of palaces and churches shook visibly. Chandeliers swayed and beds slid on the floor. Dogs barked and children cried as burglar alarms on thousands of cars were set off by the earth's movement.

Police said there were no reports of casualties in the capital, and major historical structures such as the Colosseum and the Forum appeared undamaged.

A U.S. Geological Survey spokesman at Golden, Colo. said the quake measured 5.8 on the Richter scale.

It was the strongest tremor in mainland Italy since a pair of quakes -- one measuring 6.0 and the other 5.9 on the Richter scale -- struck northeastern Italy in September, 1976, killing at least 11 persons, the spokesman said.

Just three months before that, in May, 1976, a 6.5 quake killed more than 1,000 persons in the northeastern province of Frioli. A 5.8 quake hit the island of Sicily in April 1978.

The epicenter of tonight's quake was not identified immediately, but Perugia's Seismological Institute said it was probably in the Adriatic Sea.