* Saudi's NCB, Samba among major gainers
* Dubai sees lowest trading volume in almost two years
* Summer holidays, Eid, mediocre regional economy limit activity
* Qatar down almost 10 pct since diplomatic crisis erupted in June
* Egypt's Qalaa jumps after unit divests from Ethiopian firm
DUBAI, Aug 28 (Reuters) - Banks helped nudge stock markets in the Gulf higher on Monday with Saudi Arabian lenders, which may benefit from a potential upgrade of the kingdom by index compiler FTSE at the end of next month, outperforming. Egypt firmed on buying by foreign funds.
Late next month FTSE will announce its decision on whether to include Saudi Arabia and Kuwait in its secondary emerging market index. Analysts at Arqaam Capital and EFG Hermes believe the chances are high for a positive decision in both cases.
One of Riyadh's largest listed lenders, National Commercial Bank, added 1.5 percent and Samba Financial Group rose 0.9 percent.
EFG Hermes estimates that if NCB is added to the FTSE index, and assuming implementation in two phases, it could see about $292 million of inflows while Samba's inflow could be around $203 million. The main Saudi stock index climbed 0.5 percent on Monday.
Dubai's index strengthened in the final hour of trade to close 0.3 percent higher, but daily traded volume was the lowest since September 2015 as summer holidays, the approach of a long weekend for Eid al-Adha, and a mediocre economic outlook in the region depressed activity.
Large to mid-sized stocks were some of the top gainers, with Dubai Islamic Bank adding 1.3 percent and Emaar Malls rising 1.2 percent.
Abu Dhabi's index inched up 0.1 percent in the lowest volume in three months. Large-cap developer Aldar Properties rose 0.4 percent.
Most blue-chip banks rose in Doha, including Commercial Bank , which gained 0.5 percent. The Qatar index ended a three-session loosing streak, adding 0.1 percent, but it is down almost 10 percent since Saudi Arabia, the United Arab Emirates, Bahrain and Egypt cut diplomatic and trade links with Doha on June 5.
Egypt's index regained some momentum after eight sessions of sluggish trade and rebounded 0.8 percent as international investors were net buyers, bourse data showed.
Infrastructure and energy investment firm Qalaa Holdings jumped 8.9 percent after one of its subsidiaries, Asec Co for Mining, said that it had sold its stake in an Ethiopian company in a deal worth $14.5 million.
* The index rose 0.5 percent to 7,262 points.
* The index added 0.3 percent to 3,613 points.
* The index edged up 0.1 percent to 4,485 points.
* The index added 0.1 percent to 8,941 points.
* The index rose 0.8 percent to 13,014 points.
* The index slipped 0.1 percent to 6,909 points.
* The index fell 0.1 percent to 1,301 points.
* The index rose 0.8 percent to 5,004 points. (Editing by Andrew Torchia)