(Bloomberg) — Gulf Keystone Petroleum Ltd returned all key foreign staff to Iraqi Kurdistan and will increase output after US air strikes eased the militant threat that prompted a mass evacuation of expatriate oil workers.

The explorer is on target to produce 40,000 barrels of oil a day at its Shaikan wells, it said in a statement.

Gulf Keystone has been producing about 23,000 barrels a day since August 28, the Hamilton, Bermuda-based company said.

Oil companies including Chevron Corp, Marathon Oil Corp and Afren Plc evacuated staff and halted drilling in August after Islamic State seized control of a vast swath of northern Iraq and neighbouring Syria.

ShaMaran Petroleum Corp last month resumed work at its Demir Dagh field in Kurdistan and Oryx Petroleum Corp said it would boost output in the region as the security situation improves.

Producers have also been caught in a dispute between the Kurdistan Regional Government and the central Iraqi government over how to share oil revenue.

Regional authorities have been exporting via Turkey since the start of the year against the wishes of the government in Baghdad.

Gulf Keystone is exporting about 70 per cent of its output to international markets via Turkey and selling the rest locally, it said.

It has exported about 4 million gross barrels so far and is in negotiations with Kurdish authorities about payment, according to the statement.

The company sold about 220,000 barrels of oil to local customers for about $9.4 million last month, it said.

To contact the reporter on this story: Firat Kayakiran in London at fkayakiranbloomberg.net To contact the editors responsible for this story: Will Kennedy at wkennedy3bloomberg.net Alex Devine, Dylan Griffiths