MILAN, Oct 7 (Reuters) - Eyewear tycoon Leonardo Del Vecchio has slightly raised his stake in Italy's top investment bank Mediobanca, a regulatory filing showed on Wednesday, crossing a key 10% threshold after winning regulatory approval in August.

A filing by market watchdog Consob showed Del Vecchio held 10.162% of Mediobanca as Oct. 5, up from 9.89% previously.

The founder of spectacles maker Luxottica got European Central Bank approval to raise his holding to up to 20% at the end of August. Sources had told Reuters at the time, Del Vecchio would only slightly increase his stake in the short term. (Reporting by Claudia Cristoferi and Gianluca Semeraro, editing by Valentina Za)