AN earthquake in northern Italy has killed at least six people and caused serious damage to buildings in several towns, local officials say.The magnitude-6.0 quake struck in the middle of the night, about 35km (22 miles) north of the city of Bologna.The tremor caused "significant damage to the cultural heritage” of Emilia Romagna region, the government said.Later on Sunday, a magnitude-5.1 aftershock hit the region, causing more buildings to collapse.The aftershock destroyed a clock tower and made a firefighter fall from a wall in the town of Finale Emilia, near the epicentre of the first tremor.Sunday’s quake was the worst to hit the country since the L’Aquila tremor killed nearly 300 people in central Italy in 2009. The earthquake struck at a relatively shallow depth of 10km just after 04:00 local time (02:00 GMT).It was felt across a large swathe of northern Italy, including the cities of Bologna, Ferrara, Verona and Mantua and as far away as Milan and Venice.The tremor forced many terrified residents into the streets.Two people were killed in Sant’Agostino when a ceramics factory collapsed.The mother of one of the victims told local media that "he wasn’t supposed to be there. He changed shifts with a friend”.Another person - believed to be a Moroccan national - was killed in Ponte Rodoni do Bondeno.In Tecopress di Dosso, one worker died when the roof of a foundry collapsed, Rai News24 reports.Local media also say a woman died near Bologna, with reports suggesting that she may have had a heart attack. Another victim was an elderly woman in Sant-Agostino. About 50 people were injured - but no-one seriously. More than 3,000 people were later evacuated from their homes amid fears of fresh tremors."I was woken at around 04:00 by the quake, it was strong and lasted up to a minute, maybe more,” Frankie Thompson, a UK travel journalist in Bologna, told the BBC."Church bells were set off spontaneously... followed by an eerie silence. Small aftershocks kept coming and going until maybe 05:50 when a stronger tremor shook us again but not as long and dramatic as the first,” she added.Britain’s David Trew, who is staying in a hotel in Ferrara, told the BBC: "I was sound asleep when the tremors started. I was having quite a vivid dream, and the first few seconds of the quake became part of the dream.