Volkswagen posted its first quarterly loss in at least 15 years, slammed by costs related to its rigging of diesel emissions tests, and lowered its profit outlook.

The German group on Wednesday reported a third-quarter operating loss of 3.48 billion euros ($3.84 billion), in line with a 3.47 billion-euro loss forecast in a Reuters poll of analysts.

VW set aside 6.7 billion euros in the July-September period to cover costs related to the manipulations affecting 11 million cars globally, up slightly from the 6.5 billion announced a week after the cheating became public on Sept. 18.

As a result, the German group said it now expected its operating profit to drop "significantly below" last year's record 12.7 billion euros.

Excluding costs of the scandal, the carmaker still expects its group operating margin to come in between 5.5 and 6.5 percent this year, after 6.3 percent in 2014.

Volkswagen plans to cut investments by 1 billion euros a year at its core division, which accounts for 5 million cars to be recalled. Luxury division Audi, source of about 40 percent of VW group profit, will also cut planned spending.

Volkswagen confirmed the loss it reported on Wednesday was its first quarterly loss in at least 15 years but, due to accounting changes, was unable to say precisely when the last loss occurred.

VW may need to set aside more money for measures to stabilise sales if deliveries take a hit from the scandal, Chief Executive Matthias Mueller has said. Steps could include discounts on new cars if owners turn in old models as well as cheap loans and incentives to dealers to buy back older cars.

Group deliveries, which also include premium brands Audi and Porsche, slid 1.5 percent in September to 885,300 cars and fell 3.4 percent in the third quarter to 2.39 million cars, causing VW to drop behind Japanese rival Toyota in nine-month global auto sales charts after clinching the top spot three months earlier.