BERLIN—Two companies involved in storing and supplying oil and other materials said Tuesday they have been hit by a cyberattack that has impacted operations in Germany. Oiltanking GmbH Group and Mabanaft Group on Saturday discovered what they called a “cyber incident affecting our IT systems” and launched an investigation together with external specialists, the companies said in an emailed statement. They did not elaborate on the nature of the incident or address who might be responsible, and said they are working to understand its “full scope.” They said that Oiltanking GmbH Group—which operates storage tank terminals for oil, gas and chemicals—is still operating all terminals in all global markets. But facilities at Oiltanking Deutschland GmbH, a separate entity that operates all terminals in Germany and is part of Mabanaft, are “operating with limited capacity.” Mabanaft’s German branch “has also declared force majeure for the majority of its inland supply activities …