The announcement comes as ousted leader Muammar Gaddafi remains missing and bloodshed continues to rock the North African state. Tony Buckingham, chief executive of London-listed Heritage, said his firm was "well placed to play a significant role in the future oil and gas industry in Libya".
Heritage, which operates in Iraq, the Democratic Republic of the Congo, Pakistan, Mali, Tanzania, Malta, Pakistan and Russia, said the stake was bought through wholly-owned subsidiary Heritage Energy International.
The group, which reported a 9.6 million US dollar (£6.2 million) pre-tax loss in the six months to June 30, compared with a 12.3 million US dollar (£7.9 million) loss the previous year, said it would use the Sahara Oil acquisition as a starting point for access other opportunities in Libya. The deal would give Heritage legitimate access to the rehabilitation of formerly state-run fields.
In the last five months the firm has established a base in Benghazi and said it has been in discussion with members of the National Transitional Council, the interim government in Libya.
However, a report suggested there was some confusion over whether the transfer of licences, which is overseen by the NTC, has been completed. Benghazi, Libya's second largest city, was taken by revolutionary forces in February, and has been a rebel stronghold since the conflict broke out.