DUBAI, Aug 17 (Reuters) - Stock markets in the Gulf rose early on Thursday with Saudi Arabia's index gaining strength from positive company-specific news.

The Riyadh index was up 0.4 percent in the first hour, as Atheeb Telecommunications surged 8.5 percent after it swing to a quarterly net profit of 55.4 million riyals ($14.8 million) from a loss of 58.1 million a year ago.

The result was mainly due to the sale of 500 communications towers, but also reflected an increase in data, internet and voice revenue, the company said.

"The company has been struggling for a while, especially as it competes with giants like Saudi Telecom, but I think it will manage to maintain healthy sales growth in the quarters to come," said a local telecommunications industry analyst.

Saudi Telecom fell 0.4 percent.

Saudi Basic Industries was up 0.5 percent after it announced completion of the purchase of the 50 percent that it did not already own in its petrochemical venture with Shell Arabia, a unit of Royal Dutch Shell, for $820 million.

The financial impact of the deal will be reflected in its third-quarter results.

Saudi Steel Pipes gained 3.9 percent after one of its units won a 250 million riyal ($66.7 million) contract to manufacture pipes for state oil giant Saudi Aramco.

Apparel and mall operator Fawaz Alhokair dropped 4.0 percent after it made a quarterly net profit of 232.4 million riyals, in line with NCB Capital's estimate of 231 million riyals but missing NBAD Securities' 256 million riyals forecast.

Hokair's net profit grew 4.1 percent from a year ago, but sales for the period fell 5.5 percent to 2.07 billion riyals.

Elsewhere, the Dubai index was almost unchanged with activity dominated by Union Properties , up 3.6 percent, and GFH Financial , which added 1.1 percent.

Both stocks have been volatile in recent days, GFH because of a big capital increase and Union Properties because it posted a big quarterly loss as it fixed accounting errors; the stock has now regained the level where it was trading before the announcement of the loss.

Abu Dhabi's index was up 0.1 percent as Abu Dhabi National Energy jumped 5 percent in heavy trade.

Qatar's index added 0.5 percent. Saudi Arabia said late on Wednesday it would open its Salwa border point for Qatari citizens who wished to perform the haj, but it was not clear if this signalled any movement towards resolution of its diplomatic dispute with Doha.

(Reporting by Celine Aswad; Editing by Andrew Torchia and David Holmes) ((celine.aswad@thomsonreuters.com)(+9715 62247653)(Reuters Messaging: celine.aswad.thomsonreuters.com@reuters.net))