Finnish retailer Kesko has reported a 5.7% year-on-year decline is sales to €1 billion in September.
In September, there were one fewer weekday delivery days in the grocery store than in the previous year, the company noted.
Sales of home and specialty goods at K-Citymarket also witnessed a decline.
However, the company's food service arm, Kespro reported sales growth of 2.1%.
Kesko chief executive Mikko Helander added, " In the grocery trade, the timing of campaigns and delivery dates weakened September sales."
For the period between January to September, grocery sales increased 4.9% year-on-year to €4.8 billion.
Kespro sales increased 13.3% in the first nine months, while grocery sales to K-Food stores and consumer goods trade increased 3.2% to €3.9 billion.
The retail group's sales in the construction and building technology trade declined 15.1% in local currencies, to €393.9 million.
Hardware store sales fell by 15.7% on a comparable basis, while sales of technical trade decreased by 15.0% in a comparable manner.
Excluding the sale of solar energy products, sales in the technical trade unit decreased by 9.5%.
Helander added, "In the construction and building technology trade, sales fell further due to the weakening of the construction volume, and in addition, there were one fewer delivery days than a year earlier.
"In technical trade, a large part of the decrease in sales came from solar energy products, the sales of which were exceptionally large in the comparison period due to the rapid rise in the price of electricity."