CAIRO, April 28 (Reuters) - Yields on Egyptian government bonds dropped at an auction on Thursday, data from the central bank showed.

The average yield on a 1-1/2-year zero coupon bond dropped to 14.231 percent from 14.495 percent when it was last sold on April 18.

The yield on Egypt's three-year treasury bond dropped to 14.570 percent from 14.896 percent at the last auction.

(Reporting by Asma Alsharif; Editing by Alison Williams) ((asma.alsharif@thomsonreuters.com; +20225783290; Reuters Messaging: asma.alsharif.reuters.com@reuters.net))