Its statement followed a report by German daily Handelsblatt earlier on Thursday that the planned sale by co-owners BASF and LetterOne would be examined "very intensively" by the economy ministry.

"The review of the transaction is in line with our usual and expected procedure," a company spokesperson said in an emailed statement.

When asked about the report, a ministry spokesperson declined comment because the issue concerned internal proceedings.

Under certain conditions, the German government can prohibit a company takeover, if the buyer is not from the European Union.

According to a government source, a review is not yet underway and the deal is not seen as being problematic.

Kerstin Andreae, head of German power and water utilities' lobby group BDEW, said last week that the government should watch for possible effects of Wintershall Dea's CO2 storage technology knowledge being sold, adding that in her opinion, BASF was entitled to sell Wintershall.

Harbour Energy had agreed in December to acquire the Wintershall Dea assets in the deal with BASF and LetterOne that creates one of the world's biggest independent producers.

The deal, expected to close in the fourth quarter, is in line with a number of large oil and gas acquisitions in recent months.

(Reporting by Patricia Weiss and Christian Kraemer, writing by Nette Nöstlinger and Miranda Murray; editing by Matthias Williams and Tomasz Janowski)