A powerful early morning earthquake in northern Italy has killed at least four people and toppled buildings.

Emergency services and news reports say one of the strongest earthquakes to shake the region was measured at magnitude-6.0 and sent people running into the streets.

Initial television footage indicated that older buildings had suffered damage: roofs collapsed, church towers showed cracks and the bricks of some stone walls tumbled into the street.

As dawn broke over the region, residents milled about the streets inspecting the damage.

Italy's Sky TG24 showed images of a collapsed ceramics factory where two workers were reportedly killed, and the structure had twisted metal supports jutting out at odd angles amid the mangled collapsed roof.

SKY said two other people died of apparent heart attacks.

Many people were still awake and about because it was a so-called "white night" when businesses stayed open.