At least nine earthquakes have rocked southern Italy in two hours, prompting frightened residents to sleep outdoors.

Italy's national seismology agency INGV says the strongest quake measured 5.1 and struck at 8:19 p.m. Thursday. That jolt was followed in rapid succession by eight more tremors, with the strongest measuring at 4.4.

The epicentre of the quakes was Montecilfone, a small town in Campobasso province in the south-central region of Molise.

Civil protection officials say a boy was slightly hurt after leaping off a balcony in fear, but no injuries are blamed directly on the quakes. Molise Gov. Donato Toma says some buildings suffered cracks but no major damage occurred.

The biggest jolt was felt in much of Italy's south, including in Rome and Naples.

The mayor of Montecilfone, the city near the epicentre of the largest quake, said people were scared but there was only minor damage.

"Some old walls that were already in bad shape have collapsed, but there's no major damage," Franco Pallotta said on SkyTG24.

"People are alarmed. Thank God, I have no news of injuries."

The fire department confirmed that there had been no rescue calls from the area near the epicentre, noting that only slight damage to some buildings had been spotted.