The attack on IT systems was discovered on Saturday, the Hamburg-based company announced on Tuesday. The company says it is working  to solve the problem and to determine the extent of the attack. The company is also working with external specialists and the authorities.

The attack was first reported by the Handelsblatt newspaper. According to its report Oiltanking notified its business partners that all of the company’s loading and unloading systems were affected, making the loading of tankers impossible. This cut the  petrol supply to its customers, which include medium-sized petrol stations and the oil company Shell.

“We were informed by Oiltanking over the weekend that there had been a cyberattack,” a Shell spokeswoman said. “Any potential impact on our supply chains can be offset at this stage via alternative charging points.”

According to industry sources, there is no risk of a complete breakdown of fuel supply in Germany as there are a total of 26 companies active in the market.

Ruediger Trost from the internet security company F-Secure says the cyberattack probably involves the use of extortion software, and is likely to be accompanied by a demand for money in return for a code to restore the system.

“It could then still take several days, possibly even weeks, until everything runs normally again,” he said.