Yes, according to Panasonic this works:
USB slot: Yes
Front playback
USB Standard: USB 2.0 High Speed
Playback: Xvid/ MKV/ MP4/ MPEG-2/ FLAC/ WAV/ WMA/ AAC/ MP3/ ALAC/ DSD/ JPEG/ MPO
The hard disk is only used as storage for firmware updates, nothing can be stored on it :-)