DUBAI, Oct 27 (Reuters) - Gulf stock markets may have a soft tone on Thursday as global markets sag, and after lacklustre earnings reports by some major United Arab Emirates and Qatari companies.

MSCI's broadest index of Asia-Pacific shares outside Japan is down 0.9 percent, while Brent crude oil slumped about 1 percent to around $50 a barrel overnight.

National Bank of Abu Dhabi posted a flat third-quarter net profit while First Gulf Bank reported a rise to 1.86 billion dirhams ($507 million) from 1.42 billion dirhams, partly because of gains from real estate sales. Both results were in line with analysts' forecasts and both banks posted sharply higher loan impairments.

Telecommunications operator Etisalat missed analysts' forecasts with a net profit after royalty payment of 1.9 billion dirhams; its financial statement for the corresponding period of last year stated earnings of 1.95 billion dirhams. Analysts polled by Reuters had expected a quarterly profit of 2.24 billion dirhams on average.

Qatar's Gulf International Services reported an 87 percent fall in third-quarter net profit to 28.3 million riyals ($7.8 million); QNB Financial Services had forecast 78.2 million riyals.

Aamal , a diversified investment firm, reported a 3.6 percent fall in third-quarter profit.

However, Qatar Electricity and Water Co reported a 9 percent rise in profit to 443 million riyals; that beat estimates by EFG Hermes of 412.3 million riyals and QNB Financial Services of 414.9 million riyals.

(Reporting by Andrew Torchia) ((andrew.torchia@thomsonreuters.com)(+9715 6681 7277)(Reuters Messaging: andrew.torchia.thomsonreuters.com@reuters.net))