June 10 (Reuters) - Major Gulf stock markets declined in early trading on Wednesday after the U.S. and Iran traded fresh strikes.

Iran's Revolutionary Guards said they attacked a U.S. base in Jordan and 21 other Gulf targets on Wednesday in retaliation for American strikes near the Strait of Hormuz, Iranian media reported.

The U.S. military said on X that it struck Iranian air defence systems, ground control stations and surveillance radar sites near the strait after President Donald Trump said Iran had downed a U.S. Apache helicopter on Tuesday.

The clashes mark one of the biggest exchanges in hostilities since the two countries agreed to a ceasefire in April, deepening doubts about the prospects for a deal to end the war that started on February 28.

Saudi Arabia's benchmark index .TASI fell 0.3%, hit by a 0.7% fall in Al Rajhi Bank 1120.SE and a 0.3% decrease in oil major Saudi Aramco 2222.SE.

Oil prices edged lower in volatile trade on Wednesday after notching early gains. Brent futures LCOc1 fell 9 cents, or 0.1%, to $91.36 a barrel at 0641 GMT. O/R

Dubai's main share index .DFMGI lost 0.2%, with top lender Emirates NBD ENBD.DU losing 0.9%.

In Abu Dhabi, the index .FTFADGI eased 0.2%.

The Qatari index .QSI dropped 0.3%, with the Gulf's biggest lender Qatar National Bank QNBK.QA falling 0.3%.