China National Petroleum Corp. or CNPC, the largest Chinese oil producing company, has so far invested $3.3 billion in developing oil projects in Iraq, the firm's vice president said Wednesday.

CNPC and its subsidiary PetroChina Co Ltd. are developing three large oil fields, CNPC Vice President Wang Dongjing said during the start of output at an Iraqi oil field developed by the company.

CNPC is developing along with BP PLC (BP.LN) Iraq's largest oil field, Rumaila, in the southern Basra province where production is currently hitting 1.35 million barrels a day.

CNPC is also developing Ahdab oil field in Wasit governorate in central Iraq. The field has recently started pumping 140,000 barrels a day.

Wednesday, the company commenced production for the first time of 100,000 barrels a day at Halfaya oil field in Missan province in southern Iraq.