The national cyber security authority called the victims not to react on the ransom demand. BSI also noted that they are making technical analysis and information exchange with national and international partners.
The agency did not name the companies affected, although German postal and logistics company Deutsche Post earlier said its systems in Ukraine had been affected.
BSI President Arne Schoenbohm said initial indications pointed to use of the Petya malware, which utilised the same weaknesses used in the WannaCry ransomware attack that caused global disruption in May.
BSI states the virus was spread via accountancy software M.E.Doc., developed in Ukraine.
As it was reported earlier, a computer virus wreaked havoc on firms around the globe on Tuesday, as it spread to more than 60 countries, after hitting dozens of companies and enterprises across Ukraine. The attacks began at about 11.30 a.m. on Tuesday. The provider disabled the websites of the National Police and Ministry of Internal Affairs due to cyber attack. The virus spread very quickly. It affected computers operating on Windows after restarting and coding itself.
In this regard, the National Security Council decided to strengthen the counter-terrorism and counter-intelligence measures in Kyiv and regions of Ukraine.
The criminal case on 'intervention to the operation of computers and computer networks' was initiated.