A gas flare on an oil production platform in the Soroush oil fields is seen alongside an Iranian flag in the Persian Gulf, Iran, July 25. (Xinhua/Reuters Photo)

TEHRAN, Jan. 3 (Xinhua) -- The National Iranian Oil Company (NIOC) has invited 29 international companies to participate in the country's oil and gas projects put in tenders, local media reported Tuesday.

The tenders envisage developing upstream projects in Iran's oil and gas sector, a big step to open up Iran's oil and gas fields to western investment, Iran's Petro-Egergy Information Network (SHANA) said.

To this end, the NIOC has endorsed qualification of 29 international exploration and production firms to enter partnership with Iran under new Iranian oil contracts.

The companies are from 14 countries across the world, according to SHANA.