Saudi Arabia's main stock index sank below major technical support on Monday amid heavy selling of petrochemical and resource-related shares.

After plunging 6.9 percent on Sunday, the index slowed its decline in early trade on Monday. But by mid-afternoon heavy selling pressure had resumed, with the index dropping 6.8 percent to 6,957 points, below major chart support on its December low of 7,226 points.

Saudi Basic Industries Corp, the biggest petrochemical producer, lost 6.8 percent while the petrochemical sector index plunged 8.1 percent. The sector's earnings are directly linked to falling global oil prices.

Miner Ma'aden, which rose in early trade, was down 7.4 percent.