Heritage Oil has uncovered an oilfield in Iraq's Kurdistan region that it said could yield more than 4bn barrels of oil. The news sent its shares up 25 per cent.

The announcement by the independent explorer, which comes after a year of large oil strikes in Uganda, increases the oil prospectivity of Iraq's northern autonomous region of Kurdistan. The region has attracted many other smaller oil companies including OMV, Addax and DNO. However, the discovery also draws attention to the political uncertainty surrounding oil licences in Kurdistan.