* Saudi bourse falls as investors lack encouragement to build positions
* But petrochemical stocks gain as oil breaks $50
* Dubai index gains for fourth session in a row
* Dubai Parks surges over 6 pct after raising share capital
* Egypt slips as local traders exit stock market
By Celine Aswad
DUBAI, May 26 (Reuters) - A break in Brent crude prices over $50 a barrel failed to support Saudi Arabia's index on Thursday, but helped carry Dubai's index higher for a fourth session. Other markets were mixed.
The Riyadh index failed to hold on to earlier gains as investors booked profits, snapping two days of gains.
Although petrochemical shares remained resilient, with the sub-index advancing 0.3 percent, it closed 49 points below its intra-day high, a sign that investors lack belief in a sustained rally.
Speculative shares, favoured by local day traders and which are usually heavily traded, dropped. Tourism company Altayyar Travel Group fell 2.8 percent while insurer Alinma Tokio Marine tumbled 3.1 percent.
In Abu Dhabi the index slid 0.1 percent, mainly weighed by declines in blue chip lenders National Bank of Abu Dhabi and Abu Dhabi Commercial Bank. The former closed down 2.8 percent and the latter 1.2 percent.
But Dana Gas managed to hold onto gains and climbed 1.9 percent.
Dubai's index came ahead of its peers and added 1.3 percent to 3,351 points, its highest closing level since May 2.
Dubai Park and Resorts surged 6.7 percent, and was the most heavily traded stock. Wednesday May 25 was the amusement park developer's final day of trade in its rights issue, which will increase its share capital to 8 billion dirhams ($2.2 billion).
Emaar Properties, the largest listed real estate stock, added 1.1 percent.
Qatar's stock index edged up 0.1 percent, with support from oil drilling provider Gulf International Services which closed up 2.5 percent.
Qatar National Bank, the largest lender by assets in the Gulf, rose 1.2 percent.
In Egypt, the main index slipped 0.2 percent, as locals sold off while foreign investors increased allocation to Egyptian shares, bourse data showed.
Shares in developer Amer Group fell 2.5 percent. Earlier this week the company reported a 36 percent rise in first quarter net income and a 18 percent jump in revenues from the same period last year.
"Amer Group's 1Q2016 results showcase a recovery driven by improved deliveries (of housing units) and higher recurring business contribution," said a note by Cairo-based Naeem Holding. Adding they expect moderate growth for the rest of 2016 and maintained a "buy" rating on the stock.
* The index fell 0.5 percent to 6,482 points.
* The index rose 1.3 percent to 3,351 points.
* The index edged down 0.1 percent to 4,283 points.
* The index edged up 0.1 percent to 9,716 points.
* The index lost 0.2 percent to 7,531 points.
* The index gained 0.5 percent to 5,397 points.
* The index fell 0.3 percent to 5,915 points.
* The index edged down 0.1 percent to 1,099 points.