* Egypt's Commercial International Bank continues decline
* Worries about Treasury tax change weigh on banks
* Saudi's Khodari slips after third-quarter loss widens
* 17 of 20 stocks in Qatar index rise
* Dubai Investments hits five-year low after MSCI decision
By Shakeel Ahmad and Abinaya Vijayaraghavan
Nov 26 (Reuters) - Egypt's blue-chip stock index fell for a fifth straight day on Monday, while Saudi Arabia edged up as oil prices rebounded moderately after plunging nearly 8 percent at the end of last week.
The Egyptian index, which had plunged 3.8 percent on Sunday, fell a further 0.8 percent on Monday with the country's biggest lender, Commercial International Bank (COMI) , losing 1.8 percent.
All eight traded banking stocks fell. Investors have been spooked partly by concern about authorities' proposed changes to the way banks' earnings from Egyptian Treasury bonds are calculated for tax purposes; a report released by Pharos Holding on Sunday said this would raise banks' effective tax rates, shaving 17 percent off COMI's bottom line last year.
Exchange data showed foreign investors were net sellers of Egyptian stocks by a moderate margin on Monday, while total trading volume was light.
The Saudi index edged up 0.2 percent after falling 1.3 percent in the last session. Saudi Arabia Fertilizers gained 4 percent and Banque Saudi Fransi added 2.7 percent.
But construction company Abdullah Abdul Mohsin Al Khodari Sons Co dropped 3.7 percent after reporting that its losses widened in the third quarter.
The Qatar index rose 1.0 percent, with 17 of its 20 stocks gaining. Telecommunications firm Ooredoo climbed 3.5 percent and the Middle East's largest lender, Qatar National Bank, added 1.9 percent.
Qatar General Insurance and Reinsurance Co fell as much as 5.1 percent before closing unchanged. The company said it would stop issuing new insurance policies in Dubai and wind down business at its branch there.
Abu Dhabi's index was up 0.5 percent. Telecommunications firm Etisalat added 1.2 percent and Abu Dhabi Commercial Bank gained 1.6 percent.
In Dubai, the index fell for its third straight session, losing 0.4 percent. Dubai Investments shed 3.5 percent to close at a five-year low of 1.4 dirhams; the stock has been sliding since MSCI decided earlier this month to move the company to its UAE small cap index from its United Arab Emirates standard index, effective at end-November.
SAUDI ARABIA * The index added 0.2 percent to 7,529 points. DUBAI * The index fell 0.4 percent to 2,727 points. ABU DHABI * The index rose 0.5 percent to 4,971 points. QATAR * The index rose 1 percent to 10,357 points. KUWAIT * The index added 0.5 percent to 5,294 points. EGYPT * The index fell 0.8 percent to 13,049 points. BAHRAIN * The index rose 0.5 percent to 1,327 points. OMAN * The index fell 0.7 percent to 4,393 points. (Editing by Andrew Torchia and Louise Heavens)