The quake happened at about 4:40 p.m. Sunday in an area between Massa Carrara and Lucca, Italy's ANSA news agency reported.
The tremor was followed by a 3.4-magnitude aftershock quake just after 10 p.m.
Although no damage or casualties were reported, local officials said about 400 people opted to stay in shelters created in recent days by the national Civil Protection Department and the Tuscan government.
"Almost double the number we've hosted over the two previous nights,'' said the mayor of the town of Fivizzano, Paolo Grassi. ''There were also many who slept in their cars, or in tents on their own properties ... pitched near their homes."
Sunday's tremors were the latest to follow a 5.2 earthquake that struck Italy on June 21.
That quake caused caused building damage, but no fatalities or injuries.