Stock markets in the Gulf closed down on Thursday, as fears of a possible U.S. military action against Iran raised concerns that the region would bear the brunt of any Iranian retaliation.

The deployment of a U.S. aircraft carrier and supporting warships to the Middle East this week has broadened U.S. President Donald Trump's options for potential military action, following his repeated threats to intervene over Iran's crackdown.

Saudi Arabia's benchmark index <.TASI> dropped 0.7%, ending a five-day winning streak, hit by a 1.3% fall in Al Rajhi Bank <1120.SE> and a 2.6% slide in ACWA Power.

Oil behemoth Saudi Aramco <2222.SE>, however, gained 0.6%. Crude prices, a catalyst for the Gulf's financial markets, hit a four-month high as Trump warned Iran of possible attacks if it did not make a deal on nuclear weapons.

Most sectors were lower on the day, but the losses were contained by energy, with Aramco supported by rising oil prices, said Milad Azar, market analyst at XTB MENA.

According to Azar, sentiment remains underpinned by fourth-quarter earnings and optimism ahead of next week's opening of the market to foreign investors, leaving room for further gains on strong results, firmer oil, and solid non-oil fundamentals.

Bank AlJazira <1020.SE> advanced 4.2%, its biggest intraday gain in four months, after posting a strong increase in annual net profit and proposing a 0.50 riyal-per-share cash dividend for the second half — its first in three and a half years.

In mid-January, Saudi Arabia, Qatar, Oman and Egypt urged Washington not to carry out a strike on Iran.

Dubai's main share index <.DFMGI> retreated 0.5%, weighed down by a 1.4% fall in toll operator Salik <SALIK.DU>.

In Abu Dhabi, the index <.FTFADGI> lost 0.3%, with Abu Dhabi Commercial Bank <ADCB.AD> falling 1.7%. After market hours, the lender reported a fourth-quarter net profit of 3.34 billion dirhams ($909.41 million), up from 2.57 billion dirhams a year ago.

The UAE said on Monday it would not allow its airspace, territory, or waters to be used for hostile military action against Iran, reaffirming its neutrality and commitment to regional stability.

The Qatari index <.QSI> finished 0.6% lower, with Qatar National Bank <QNBK.QA>, the Gulf's biggest lender by assets, sliding 1.3%.

The Egyptian bourse was closed for a public holiday.

(Reporting by Ateeq Shariff in Bengaluru; Editing by Janane Venkatraman and Shilpi Majumdar)