The group said it does not see an early end to the chip crunch that has forced automakers to halt or reduce production.
"As there is no sign soon of a resolution of this situation, we expect a volatile sales situation and the market to further decrease in the next few months," AEB Chairman, Thomas Staertzel, said in a statement.
Sales of Lada, Russia's top-selling brand, fell 32 percent last month, while No. 2 Kia was down 13 percent.
Third-place Hyundai fell 19 percent and No. 4 Renault's volume dropped by 11 percent.
Toyota, the No. 5 brand by sales, dropped 4 percent. Volkswagen, at No. 6, fell 41 percent.