This has just been published by Eurocontrol in the last few minutes.
In summary, flights moving through the nearby area as well as those upwind of volcanic ash output may expect re-routing and delays.
These delays will most affect travel in proximity of Catania-Fontanarossa Airport (LICC/CTA), with delays of up to 50min expected for planes arriving into this airfield.
I'm sure more news will come to hand as the situation develops.
05/01/2012 - Volcanic ash contamination
AO's please be informed, that ETNA volcano has erupted. The following 2 NOTAMs refer:
M0071/12 and A0047/12.
We have applied an arrival regulation at LICC between 1300 and 1800 UTC today (reg. ID LICCA05), delays are up to 50 minutes.
Some tactical re-routing will probably also take place in order to avoid the ash cloud.
DNM NOS Brussels