DUBAI, July 6 (Reuters) - Shares in Saudi Arabia's cement and steel sectors surged in early trade on Thursday after the government cut export tariffs, but Gulf stock markets were mostly weak after a slide in oil prices.

The Saudi government said it was cancelling all export duties on steel for two years to encourage local industries, and would slash cement export tariffs by 50 percent.

Najran Cement jumped 6.2 percent in unusually high volume and was the top gainer in Riyadh after 35 minutes of trade. All other stocks among the top 10 gainers were also from the building materials sector, including Al Yamamah Steel Industries , which rose 2.1 percent.

Building materials producers have been hurt hard in the past couple of years by a construction industry slump caused by the government's austerity policies.

Qatar's index fell 0.5 percent. Four Arab states decided in a meeting in Cairo on Wednesday not to slap fresh sanctions on Qatar for now, but voiced disappointment at its "negative" response to their demands and warned of the possibility of further action against Doha.

In Dubai the index was down 0.5 percent, hit by a 1.4 percent drop in shares of blue chip Emaar Properties and a 0.9 percent fall in peer DAMAC Properties

In Abu Dhabi, Dana Gas fell 1.4 percent after sources told Reuters that London's High Court planned to hold a full hearing in September on efforts by the company to restructure $700 million of its Islamic bonds.

A High Court judge upheld an interim injunction there blocking holders of the sukuk, due to mature in October, from enforcing claims against Dana. But he also ordered Dana to cancel an injunction in a court in the emirate of Sharjah and seek a stay of its proceedings there.

The Abu Dhabi index was down 0.6 percent.

(Reporting by Celine Aswad; Editing by Andrew Torchia) (( 62247653)(Reuters Messaging: