DUBAI, Aug 15 (Reuters) - Gulf stock markets were mostly slugggish in early trade on Tuesday with Union Properties plunging after it reported a 2.29 billion dirham ($624 million) net loss for the second quarter.

Union Properties said it was taking big provisions to cover past accounting errors related to its booking of a 503 million dirham gain on a plot of land at Dubai's Motor City.

The errors were discovered as a new board and senior management, appointed in May, conducted an investigation of accounting practices dating back to 2013, the company said; its stock sank 7.9 percent to 0.789 dirham. Trading volume in Union Properties was about half half the market's entire volume.

The stock dropped below technical support at its February low of 0.852 dirham, triggering a bearish right triangle formed by the highs and lows since January and pointing down to around 0.60 dirham.

Dubai's stock index edged down 0.2 percent. The biggest real estate developer, Emaar Properties, rose 0.6 percent after reporting a 14.4 percent increase in second-quarter profit that was roughly in the middle of analysts' forecasts.

GFH Financial climbed 1.7 percent after tumbling 10 percent on Monday. On Tuesday morning, it said it had completed the acquisition of a $1.2 billion infrastructure portfolio in Africa and the Middle East, funded by a $315 million capital increase that took issued and paid-up capital to $975 million.

But restaurant and retail investment firm Marka sank 5.9 percent after reporting a second-quarter loss attributable to shareholders of 126 million dirhams ($34.3 million) versus a year-ago loss of 18.7 million dirhams.

Abu Dhabi's index rose 0.2 percent on the back of a 3.7 percent surge by Eshraq Properties .

But Saudi Arabia's index edged down 0.1 percent. Insurer MedGulf , which has been falling sharply this week after reporting a big second-quarter loss, slid a further 2.3 percent. Wafa Insurance, which earlier this month reported lower quarterly profit, fell 2.8 percent.

Qatar's index dropped 0.4 percent as Gulf Warehousing lost 1.8 percent. But Investment Holding Group , which tumbled 13 percent from its initial public offer price on Monday as it listed on the market, rebounded 1.2 percent.

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