Baghdad's top energy official inaugurated a giant oilfield in south Iraq on Wednesday, with a group of Chinese, French and Malaysian firms set to pump 535,000 barrels of oil a day there within five years.

The official opening of the Halfaya field in Maysan province comes after Iraq signed three preliminary energy exploration deals with foreign firms, and with the country looking to ramp up oil output.

"Halfaya oil field was opened today by the deputy prime minister responsible for energy affairs, Hussein al-Shahristani," his spokesman Faisal Abdullah said.

"This marks the inauguration of Halfaya, which was discovered in 1979."

"They (the consortium) started pumping in June, and during the last three weeks they were continuing to pump, but the official opening of the oilfield is today."

Halfaya had been pumping around 70,000 barrels per day (bpd) for about three weeks in an initial phase, but China's CNPC, Malaysia's Petronas and France's Total are to up production to 535,000 bpd by 2017.

CNPC, Petronas and Total won the contract to raise production at Halfaya in a public auction for international energy firms in December 2009.

They will receive $1.40 per barrel of oil extracted from Halfaya, which has known reserves of 4.1 billion barrels of oil.

CNPC has the biggest stake in the consortium at 37.5 percent, followed by Petronas and Total at 18.75 percent each, with Iraq's state-owned South Oil Company holding a 25 percent stake.

Oil sales account for the vast majority of Iraqi government income and around two-thirds of gross domestic product. Iraq is seeking to significantly boost its oil output, which currently stands at more than 3 million bpd.