DUBAI, Oct 13 (Reuters) - National Bank of Oman NBO.OM (NBO), the sultanate's third-largest lender by assets, posted on Thursday a 15.2 percent fall in third-quarter net profit according to Reuters calculations, missing analysts' expectations.

The lender made a net profit of 12.70 million rials ($33.0 million) in the three months to Sept. 30, Reuters calculated based on previous financial statements in lieu of a quarterly breakdown.

This was down from 14.97 million rials in the same period last year.

Three analysts polled by Reuters forecast an average quarterly net profit of 15.02 million rials. ($1 = 0.3846 Omani rials)

(Reporting By Tom Arnold; editing by Susan Thomas) ((Tom.Arnold@thomsonreuters.com; +97144536265; Reuters Messaging: tom.arnold.thomsonreuters.com@reuters.net))