The Iranian parliament has approved a bill calling for the protection of foreign investmnts in the country's free trade zones.

The law guarantees investments in areas such as the Gulf islands of Kish and Qeshm and Chabahar port on the Oman Sea, even in the event of a nationalisation drive.

Only 43 foreign firms are currently active in the zones, with investments below $15m.

Iran, which has been hit hard by falling oil prices, has been trying to attract foreign investment in an attempt to revive its economy.