July 23 (Reuters) - Major Gulf stock markets were mixed in early trading on Thursday, as investors assessed escalating tensions in the region and a range of corporate results.

The US military announced Wednesday that it had launched another round of strikes on Iran at the direction of President Donald Trump, marking the twelfth consecutive night of US attacks.

Iran's Revolutionary Guard said a fire broke out on an oil tanker after an explosion occurred as it tried to sail through what it described as a minefield in the southern Strait of Hormuz, near the coast of Oman, while two other tankers turned back.

The Saudi benchmark index fell 0.1 percent, weighed down by a 0.9 percent drop in shares of the country's largest bank, National Bank of Saudi Arabia.

However, shares of Saudi oil giant Aramco rose 0.5 percent.

Tensions escalated further after the Iran-aligned Houthi rebels announced on Thursday that they had attacked two Saudi oil tankers in the Bab al-Mandab Strait, raising concerns about a potential threat to another major global energy shipping lane besides the Strait of Hormuz.

The index in Qatar fell 0.3 percent, with shares of Qatar Petrochemical Industries Company declining 1.2 percent.

Dubai's main index rose 0.6 percent, boosted by a 2.9 percent gain in shares of Emirates NBD, the emirate's largest bank. The bank reported that its second-quarter profits were flat compared to the previous quarter, its first full-quarter results since the start of the Iran-Iraq War.

In Abu Dhabi, the index rose 0.7 percent, supported by a 2.9 percent jump in shares of the UAE's largest bank, First Abu Dhabi Bank, following a rise in its quarterly profits.

The bank's net profit for the quarter ending June 30 increased to AED 5.72 billion ($1.56 billion), compared with AED 5.51 billion in the same quarter a year earlier.