Seplat Petroleum Development Co Plc confirmed that it was interested in British oil producer Afren Plc. Seplat said it could not provide more details as the approach was preliminary.
Afren first disclosed in December that the Nigerian oil and gas explorer had made a bid to acquire it.
Seplat has until Jan. 19 to make a firm offer.
Afren’s shares were down slightly at 39.30 pence at 1235 GMT on the London Stock Exchange.