Saudi Arabia's stock market rose in early trading on Sunday ahead of their inclusion in FTSE Russell and S&P Dow Jones emerging market indexes on Monday, which are expected to attract billions of dollars in passive funds.
Saudi stocks initially joined the two indexes earlier this year.
Saudi stocks will see fourth tranche inclusion in FTSE Russell and the second and final tranche entry into S&P Dow Jones as an emerging market starting on September 23.
Saudi Arabia's index was up 0.3%, extending its gains for a straight third day. Al Rajhi Bank rose 1%, while Saudi British Bank was up 1.3%.
Saudi Basic Industries (SABIC) 2010 inched up 0.3%. The firm said last week that its feedstock supplies from Saudi Aramco have significantly improved and are likely to return to normal by end of September.
But, the tensions in Middle East weighed on other Gulf markets.
A Saudi official said Riyadh would consider the attack on Saudi Arabian oil facilities as an act of war if investigation showed the attack was launched from Iranian territory.
Qatar's index eased 0.4% as most of banking shares traded in negative territory. The Gulf's largest lender Qatar National Bank fell 1.9%.
In Abu Dhabi, the index was down 0.3% with First Abu Dhabi Bank and Emirates Telecommunications Group falling 0.4% and 0.5% respectively.
Dubai's index slipped 0.2% to extended its losses to a straight fourth day. Dubai's largest listed developer Emaar Properties dropped 1.4% and its unit Emar Malls shed 2.1%.
(Reporting by Maqsood Alam in Bengaluru Editing by Raissa Kasolowsky) ((Maqsood.Alam@thomsonreuters.com;))