Iraq plans to hold an auction of gas exploration blocks open to international energy companies later this year, the fifth of its kind since 2009, a spokesman said on Sunday.

Baghdad will offer 10 exploration blocks in the auction, the date of which has yet to be finalised, oil ministry spokesman Assem Jihad told AFP.

"The date will be announced after all the documents are finalised," he said. "It will be a good auction, and it will attract international companies to bid."

Iraq has held four previous bid rounds, including one in May 2012 for oil and gas exploration blocks that was widely viewed as a flop as foreign firms largely did not bid because of what were seen as unfavourable contract terms.

Oil Minister Abdelkarim al-Luaybi said this month that Iraq plans to invest $173 billion in its energy infrastructure, including its gas production and storage facilities, over the next five years.

Iraq has proven reserves of 143.1 billion barrels of oil and 3.2 trillion cubic metres (111.9 trillion cubic feet) of gas, both of which are among the largest reserves in the world.

Baghdad is almost entirely dependent on energy sales for much-needed revenues to rebuild Iraq's decrepit infrastructure and state-dominated economy, both of which have been shattered by decades of conflict and sanctions.

It has sought in recent years to sign contracts with international energy firms in order to boost output sharply and cement its role as a key global oil supplier.