The Saudi index started the week on a strong note climbing to an eight month closing high as investors expect strong company results.
The benchmark rose 0.5 per cent to end at 6,730 points, its highest close since May 2010.
The petrochemical index gained 0.7 per cent, as Saudi Fertilizers Company (Safco) climbed 2.8 per cent.
Saudi Arabian Mining Company (Maaden) surged 7.4 per cent.
"The rise in petchems today was only on a number of petrochemical stocks. I don't think this rise will continue," Hesham Abou-Jamee of Bakheet Investment Group told Al Arabiya television.
"We are still waiting for good financial results to be reported that will support a rise in prices. As for Maaden's rise, that was all speculation. There was no new news on the company so perhaps tomorrow we will see a negative reaction to the share price," he said.