Iran's official IRNA news agency quoted an informed Oil Ministry source on Tuesday saying Iran had found a gas field of about 200 billion cubic metres (seven trillion cubic feet) under Lavan island in the Gulf.
The news comes within a week of Oil Minister Bijan Zanganeh saying a new field had been discovered, details of which he would announce later.
IRNA's source said another field of uncertain volume had been discovered close to Balal, also in the Gulf, but cautioned it was unclear whether that was just a pocket of the giant South Pars field.
Iran has the world's second largest reserves of natural gas but development of fields and exports have been slow.