COPENHAGEN (Reuters) – Danish supermarket chains Bilka and Fotex said their websites had been taken down by cyber attacks at the launch of their Black Friday sales campaigns.

The websites were hit by “malicious cyber-connection” attacks, an advanced form of a Distributed Denial of Service (DDoS) attack where hackers send numerous requests to refresh the websites, causing them to crash, a spokesman of Dansk Supermarked A/S, the owner of both chains, said.

However, the hackers were not attempting to obtain data from the company or its customers, and it was too early to say how sales would be impacted on one of the biggest shopping days of the year, he added.

Dansk Supermarked, the country’s second largest supermarket retailer with a market share of around one-third, owns and operates 100 Fotex supermarkets and 18 Bilka hypermarkets in Denmark.

It also runs Netto discount retail shops in Germany, Poland and Sweden. Netto was not affected by the cyber attack.

Earlier this month, A.P. Moller-Maersk (MAERSKb.CO) agreed to sell its remaining 19 percent stake in Dansk Supermarked to Salling Companies for 5.53 billion Danish crowns ($882 million).

Maersk itself faces a bill of up to $300 million after the Petya cyber attack in June severely hit its container shipping business and port operations.

($1 = 6.2696 Danish crowns)