FRANKFURT (Reuters) - German utility RWE <RWEG.DE> is asking potential buyers of its oil and gas unit DEA <RWEDE.UL> to submit offers by late December in a deal that could fetch up to 5 billion euros (4.2 billion pounds), three people familiar with the matter told Reuters.

Wintershall, the oil and gas arm of German chemicals group BASF <BASFn.DE>, has been the only group to publicly express interest in DEA so far.

Private equity investors such as KKR <KKR.N> and Blackstone <BX.N> are also likely to hand in bids, while British energy supplier Centrica <CNA.L> is expected to show interest as well, the sources said.

RWE, KKR, Blackstone and Centrica all declined to comment.

(Reporting by Arno Schuetze and Christoph Steitz; Additional reporting by Alexander Huebner in Frankfurt, Aizhu Chen in Beijing, Dinesh Nair in Dubai and Sarah Young in London; Editing by Jonathan Gould)