Hundreds of people left their newly repaired homes in L'Aquila Monday night and slept in their cars after a 4.5 Richter magnitude quake revived memories of the 5.8 tremor that devastated the area in April.
Many people also returned to tents as aftershocks hit the Abruzzo capital through the night.
No one was hurt but some parts of shaky buildings are being inspected.
Worried quake victims said fresh tests should be made in homes that officials have cleared for people to reoccupy.
Some 300 people were killed and 60,000 left homeless by the April 6 quake, Italy's biggest natural disaster in 30 years.
Premier Silvio Berlusconi has promised the homeless will be given permanent homes before winter.
He also moved the July 8-10 Group of Eight summit to the city to help boost morale and get the local economy back on its feet.
