Following this announcement, shares of JKX Oil & Gas jumped as much as 45% on Thursday.

The announcement at the stock exchange, however, also carries a customary warning that states "there can be no certainty that a firm offer will be made nor as to the terms on which any offer might be made."

With principal oil and gas assets located in Ukraine and Russia and additional assets in Hungary and Slovakia, JKX Oil & Gas operations cover the full-cycle E&P value chain of exploration, appraisal, and development through to production.

In 2013, the firm’s daily production averaged 9,731 boepd and at 31 December 2013, the firm had 2P oil and gas reserves of 94.2 MMboe — including 542.7 Bcf of gas and oil reserves of 3.7 MMbbl.