Staffing levels in the northern Kurdish region of war-torn Iraq are back at normal levels, Gulf Keystone Petroleum announced Wednesday.

Militants with the group calling itself the Islamic State have taken over parts of northwestern Iraq and northeastern Syria. The rise of the group earlier this year prompted oil companies operating in the region to pull non-essential staff from Iraq as a security precaution.

Gulf Keystone, which has headquarters in London, said staffing levels in the Kurdish north of Iraq have been at normal levels since the beginning of September.

"With all personnel now back in country, we are making good progress and look forward to reaching our target of 40,000 gross barrels of oil per day," John Gerstenlauer, Gulf Keystone's chief executive officer said.

The company said production has held steady at around 28,000 bpd since August. About 70 percent of its production is sent by truck across the Iraqi border to Turkey for sales to the international market.

Around 4 million barrels of oil taken from the company's Shaikan field in the Kurdish north of Iraq have been sold on the international market since January.

The semiautonomous Kurdistan Regional Government and the central government in Baghdad are at odds over who has the right to export oil.