CAIRO, Aug 24 (Reuters) - Average yields on Egypt's six-month and one-year treasury bills fell at an auction on Thursday, central bank data showed.

Average yields on the 182-day bill fell to 19.345 percent from 19.368 percent at the last sale on Aug. 17, and yields on the 357-day bill fell to 19.015 percent from 19.308 percent, the data showed.

The combined foreign contribution in the tenors on Thursday amounted to 5.7 billion Egyptian pounds ($322.58 million), the head of public debt at the finance ministry, Sami Khallaf, told Reuters.

Demand for Egypt's domestic debt has increased since the central bank floated its pound currency in November as part of an International Monetary Fund loan agreement aimed at reviving the economy.

The central bank has raised its key interest rates by 700 basis points since the pound float but kept them unchanged in a policy meeting last week.

Total foreign holdings in Egyptian securities stood at 279.5 billion Egyptian pounds as of August 22, a 3 percent increase from a week earlier, Khallaf said.

($1 = 17.6800 Egyptian pounds)

(Reporting by Eric Knecht; Writing by Ahmed Aboulenein; Editing by Susan Thomas and Jane Merriman) ((ahmed.aboulenein@thomsonreuters.com; +20 2 2394 8097; Reuters Messaging: ahmed.aboulenein.thomsonreuters.com@reuters.net))