July 8 (Reuters) - Major Gulf stock markets declined on Wednesday, as renewed fighting in the Middle East and fresh U.S. sanctions on Iranian oil raised doubts over the durability of the ceasefire.

The United States said it had struck Iranian air defence systems, coastal surveillance facilities and drone launch sites, while Iran's Revolutionary Guards said they had targeted U.S. military positions in Bahrain and Kuwait, where air raid sirens sounded on Wednesday.

Washington also moved to revoke a waiver that had allowed Iran to sell oil on the global market, a move Iran's foreign ministry said violated the framework agreement aimed at ending the war.

A Qatari LNG tanker was in danger of exploding and a Saudi crude tanker sustained damage near the Strait of Hormuz on Tuesday, driving oil prices higher. Maritime authorities raised the threat level for vessels transiting the waterway to "severe."

Brent crude futures LCOc1 was up 3.2% at $76.56 a barrel at 0645 GMT. O/R

Saudi Arabia's benchmark index .TASI eased 0.2%, with Al Rajhi Bank 1120.SE falling 0.3%. However, oil major Saudi Aramco 2222.SE firmed 0.5%.

Dubai's main share index .DFMGI declined 1%, dragged by a 1.2% slide in blue-chip developer Emaar Properties EMAR.DU and a 1.4% drop in Sharia-compliant lender Dubai Islamic Bank DISB.DU.

In Abu Dhabi, the index .FTFADGI fell 0.7%, with Alpha Dhabi Holding ALPHADHABI.AD losing 1.6%.

The Qatari index .QSI was down 0.4%, with the Gulf's biggest lender Qatar National Bank QNBK.QA slipping 0.4%.