ROME -- A car plowed into pedestrians in the northern Italian city of Modena on Saturday, injuring eight people, four of them are in serious condition, according to Italy's ANSA news agency.

Modena Mayor Massimo Mezzetti told local media that the driver, a 31-year-old man, drove onto a sidewalk in the central city, hitting several pedestrians before crashing into a shop window.

Witnesses said the driver finally got out of the car and stabbed a passerby who had tried to stop him.

The driver has been detained and is being questioned at police headquarters.

Italian Prime Minister Giorgia Meloni described the incident as "extremely serious" in a social media post, adding that she is in contact with local authorities.

Emergency services, including police, the national gendarmerie and the financial police, have arrived at the scene. An investigation is underway.