Iran has begun negotiations to buy shares in oil refineries in Europe, Latin America and Asia, a deputy oil minister was quoted as saying by Mehr News Agency on Tuesday.
"Buying the oil refineries abroad or their shares is Iran's policy following the lifting of sanctions," said Abbas Kazemi, head of the National Iranian Oil Refining and Distribution Company.
Under a deal reached with six major powers in July, Iran agreed to modify its nuclear program in exchange for an end to economic sanctions imposed on the country in 2012.
Kazemi said that Tehran was in talks to buy a stake in India's Essar Oil, although this was denied by India's second-largest private refiner.
"Essar has signed a non-binding term sheet with (Russian refiner) Rosneft for exclusive negotiations in relation to sale of Essar Oil shares and there is no other discussion in this regard," an Essar spokesman said.
In July, Rosneft signed a preliminary deal to acquire up to 49 percent of Essar.
India is Iran's second-largest customer after China.
Iran's oil production has fallen to 2.7 million barrels per day (bpd) — down by one million bpd since the start of 2012.
Kazemi said the National Iranian Oil Company (NIOC) was willing to invest in plants to refine Iran's crude oil as this would be more economical for the country.
The OPEC member aims to raise oil output by 500,000 bpd as soon as the sanctions are lifted in early 2016 and by one million bpd from March.
Iranian officials have said Asian markets would be Iran's priority for selling oil once the sanctions are removed.