Stock markets in Gulf were weak in early trade on Tuesday with Saudi Arabia's index heading for its third straight session of declines after oil prices fell to three-week lows overnight. The Riyadh index .TASI was down 0.5 percent after 35 minutes; 12 of the 14 listed petrochemical shares declined after Brent crude futures LCOc1 retreated 4 percent on Monday. The biggest petrochemical producer, Saudi Basic Industries 2010.SE, fell 0.3 percent. Telecommunications operator Zain Saudi 7030.SE fell 1.2 percent after announcing it would not appeal a 219.5 million riyal ($58.5 million) judgement against it in a legal dispute with rival Mobily 7020.SE. Zain said the payment would have no impact on its financials as it already booked provisions. Mobily 7020.SE was down 1.4 percent after the company announced it had appointed Ahmed Abdelsalam Abdelrahman to replace chief executive Ahmad Farroukh. Qatar's index .QSI fell 0.3 percent with petrochemical producer Industries Qatar IQCD.QA pulling back 1.6 percent. Dubai's index DFMGI edged down only 0.3 percent to 3,711 points as some of the top gainers from the previous session were sold. Ajman Bank AJBNK.DU, which jumped 7.8 percent on Monday, retreated 3.0 percent. The index is technically bullish after confirming a break in the last two days above resistance at the mid-December peak of 3,659 points. That level is now support. In neighbouring Abu Dhabi, the index .ADI was flat with some large-cap banks making small gains. National Bank of Abu Dhabi NBAD.AD was up 0.5 percent.