The world's fourth-biggest petrochemical firm, Saudi Basic Industries, soared 4% after its joint-venture with China's SINOPEC kicked off its ethylene expansion project on October 14.
In Dubai, the index fell 1.6%. Emirates NBD saw its worst session in nearly eight months and closed down 3.8%.
The bank's board approved a capital increase via a rights issue of up to 6.45 billion dirhams ($1.76 billion), lower than 7.35 billion dirhams that the general assembly had decided in February this year.
Deyaar Development shed 5.6% after the developer reported a sharp decline in its third-quarter profit compared with the same quarter a year earlier.
Qatar's index slipped 0.1% as banking and energy stocks weighed. Qatar Fuel and Qatar Islamic Bank lost 1.3% and 0.7%, respectively.
Separately, Qatari company Baladna, which has built a dairy business in the desert following a trade embargo by Saudi Arabia and its allies, will launch an initial public offering this month that could raise 1.43 billion riyals ($392.86 million).
Meanwhile, Abu Dhabi's index reversed its course to close 0.1% higher, helped by a 1.4% rise in Aldar Properties.
On Wednesday, the realtor's unit issued a $500 million sukuk, or Islamic bonds, and the transaction was six times oversubscribed.
Egypt's blue-chip index traded flat with country's largest lender, Commercial International Bank, dropping 1%, while developer Madinet Nasr ended 6% higher.