Europe is proving to be the core battleground in Iranian attempts to regain market share amid bumper exports from rival producers Saudi Arabia and Iraq – both of which are also developing new European markets.

Opec heavyweights and political rivals Iran and Saudi Arabia have a long history of competing for market share both in Europe and the Far East. Tehran was hit hard by the imposition of international sanctions in 2012, but it has been making moves since they were removed in late...