CAIRO, Aug 21 (Reuters) - Yields on Egypt's three-year treasury bonds rose while yields on the seven-year bonds dropped at an auction on Monday, data from the central bank showed.

The average yield on the three-year bonds dropped to 16.804 percent on Monday from 16.813 percent at the last auction. The seven-year bond yield rose to 16.983 percent from 16.750 percent.

(Reporting by Amina Ismail; Editing by Keith Weir) ((amina.ismail@thomsonreuters.com; +20 2 2394 8114;))