But market heavyweight Saudi Basic Industries dropped 1.4 percent as it traded ex-dividend. The Abu Dhabi index fell 0.4 percent, led by 1.1 percent fall in First Abu Dhabi Bank (FAB) and 1.6 percent slide in Abu Dhabi Islamic Bank. Last week, the banks denied they were in merger talks after a news report said the emirate was considering combining them. On Monday, Qatar filed lawsuits against three banks including First Abu Dhabi Bank, accusing the trio of overseas currency manipulation which caused billions of dollars of damage to Qatar's economy.