CAIRO, June 19 (Reuters) - Average yields on Egypt's five-year and 10-year treasury bonds dipped at an auction on Monday, central bank data showed.

Average yields on the five-year bonds fell to 18.349 percent from 18.475 percent at the last auction on June 5, while the yield on the 10-year bond fell to 18.346 percent from 18.556 percent.

(Reporting by Arwa Gaballa) ((arwa.gaballa@thomsonreuters.com; +20 2 2578 3290;))