The figure is up steeply compared to 296 deaths on Wednesday.
The number of cases in the region, which includes Italy's financial capital Milan, increased by some 2,543 to roughly 34,890, the source said. On Wednesday, 1,643 new cases were registered.
The nationwide tally will be released around 6.00 p.m. (1700 GMT). On Wednesday, the national death toll stood at 7,503, the highest in the world.