The five-hour attack began in the evening of 16 March 1988, following a series of indiscriminate conventional (rocket and napalm) attacks. Iraqi Su-22 and Mi-8 aircraft began dropping chemical bombs on Halabja's residential areas, far from the besieged Iraqi army base on the outskirts of the town. According to regional Kurdish rebel commanders, Iraqi aircraft, coordinated by helicopters, conducted up to 14 bombings in sorties of seven to eight planes each. Eyewitnesses told of clouds of white, black and then yellow smoke billowing upward and rising as a column about in the air.