Other petrochemical makers were also weak after Brent crude slipped below $51 a barrel overnight to its lowest close this year. Riyadh's stock index lost 0.6 percent in modest trading volume.
The prince said the government would focus on investing in the mining sector, developing the weapons industry, supporting growth of an auto industry and improving the kingdom's logistics, both sea and air.
He also said authorities would announce a programme to address Saudi Arabia's shortage of private housing in the third quarter of this year. But he did not give a time frame or expected expenditure on those projects.
Among companies that could benefit from the government's industrial investment, Emaar the Economic City edged up 0.3 percent, extending the previous session's 4.6 percent gain, but Saudi Automotive Services
gave back most of Tuesday's rise and fell 2.9 percent.
Saudi Mining Co (Ma'aden) the only listed company directly involved in mining, edged up 0.5 percent. National Metal Manufacturing and Casting rose 0.7 percent.
Small ground freight and logistics company Batic Investments and Logistics added 1.4 percent in active trade.
Elsewhere, Dubai's index edged down 0.5 percent as Bahraini investment firm GFH Financial slumped 8.9 percent. The company reported quarterly net income attributable to shareholders of $31.91 million, up from $6.06 million a year earlier, but the stock had already risen sharply over the past week in anticipation of strong earnings.
Twenty-two other shares declined in Dubai, including builder Arabtec , which fell 2.4 percent.
In Abu Dhabi, the index rose 0.6 percent as the largest listed lender, First Abu Dhabi Bank , climbed 1.4 percent.
Qatar's index lost 0.4 percent to a five-month low as telecommunications operator Ooredoo
dropped 2.3 percent. Its Omani unit looks set to face fresh competition after Abu Dhabi's Etisalat joined Saudi Telecom and Kuwait's Zain Group in bidding for Oman's third mobile licence.
Kunal Damle, senior institutional sales broker at SICO Bahrain, said all the bidders had a strong cash position and would not need to raise debt to operate in Oman. He believes Saudi Telecom and Zain stand the best chances of winning.
"From a consumer's standpoint, Oman would be better off with the product offering from STC's VIVA brand. However, the decision may hinge on the fact that Kuwait is a big investor in the sultanate," Damle added.
At present, Oman Telecommunication and Ooredoo
Oman both have equal market shares of around 41 percent. Omantel was flat on Wednesday while Ooredoo
Oman lost 0.4 percent.
The Egyptian index added 0.6 percent in thin trade with declining stocks in the broad market outnumbering gainers by 93 to 71.
* The index fell 0.6 percent to 6,968 points.
* The index lost 0.5 percent to 3,419 points.
* The index added 0.6 percent to 4,581 points.
* The index fell 0.4 percent to 9,955 points.
* The index added 0.6 percent to 12,604 points.
* The index gained 0.6 percent to 6,799 points.
* The index lost 0.6 percent to 1,331 points.
* The index edged down 0.3 percent to 5,492 points. > (Editing by Andrew Torchia) ((firstname.lastname@example.org)(+9715 6224 7653)(Reuters Messaging: email@example.com))