Saudi Arabia's stock market rose on Wednesday,  lifted by Advanced Petrochemical, while political concerns continued to weigh on most other Gulf markets.

Saudi's index was up 0.4% after snapping a four-day losing streak in the last session.

Advanced Petrochemical rose 5.9% after its Advanced Global Investment unit won a Government project to set up petrochemical plants for an estimated cost of $1.8 billion.

Banks also advanced, with Banque Saudi Fransi gaining 1.2% and Riyad Bank adding 1%.

But other Gulf markets mostly fell on mounting political concerns.

U.S. President Donald Trump threatened on Tuesday to obliterate parts of Iran if it attacked "anything American," but left the door open for talks, saying that Iran should speak to the United States "peaceably" to ease tensions and potentially lift U.S. economic sanctions.

Kuwait's premier index opened higher after its stocks were upgraded by MSCI, but weak regional sentiment pushed it down 0.8%.

MSCI Inc said on Tuesday it would upgrade Kuwaiti equities to its main emerging markets index in 2020, a move that could trigger billions of dollars of inflows from passive funds.

The Kuwaiti market has outperformed markets in the Middle East in anticipation of the MSCI move and has risen about 20% so far this year.

The Abu Dhabi index was down 0.5% with Emirates Telecommunications Group shedding 0.5% and First Abu Dhabi Bank slipping 0.3%.

Dubai's index also edged down 0.1% as Dubai Islamic Bank shed 0.6%.

However, investment firm Shuaa Capital climbed 4.5% after it agreed terms of merger with Abu Dhabi Financial Group.

Qatar's index traded 0.1% higher, lifted by a 0.8% rise in petrochemical maker Industries Qatar and a 0.4% gain in Qatar National Bank.

Industries Qatar split its stock on Wednesday after banks having their stocks split earlier this month.

A ten-to-one stock split for companies on the exchange is being phased in from June 9, in a bid to boost liquidity by encouraging smaller investors to buy shares.