MILAN, Oct 1 (Reuters) - Italian car sales fell 25.37 percent year-on-year to 124,976 vehicles in September, the transport ministry said on Monday, as a change towards tougher emissions tests weighed on sales.

The drop came after the tougher new Worldwide Harmonised Light Vehicle Test Procedure (WLTP) became mandatory from the start of September, forcing some carmakers to clear inventory of older models in August via discounts.

Italian car sales rose 9.5 percent in August.

Fiat Chrysler's market share stood at 22.7 percent in September, down from 27.1 percent the previous month, according to Reuters calculations.

(Reporting by Agnieszka Flak)