The witness, Kurdish villager Ali Mustafa Hama, said he saw between eight and 12 planes in the sky.
"They bombarded Balisan and Sheikhwesan villages," Hama said. "The sound of the blasts was different from other [bombs]. The sound of the blasts was lower than the usual bombs. There was light green smoke rising above Balisan. After that, [the smoke] started burning people's eyes and people began vomiting."
Defense attorneys contended the campaign targeted Iranian-backed rebels.
Hussein and six senior aides are charged with offenses related to the Anfal campaign against Iraq's Kurdish minority, which prosecutors say led to the death of 182,000 civilians.
The trial was adjourned after nearly six hours and will resume on August 23.
If convicted, the deposed Iraqi president could get the death penalty.
The new case begins as Hussein and other associates await a verdict in a previous trial on charges of killing 148 Shi’a following a 1982 assassination attempt against him.