Iraq's top energy official repeated claims on Tuesday that the country's autonomous Kurdish region was "illegally" exporting oil, the latest in a long-running dispute between the two sides.

The remarks from Hussein al-Shahristani, the deputy prime minister responsible for energy affairs, come as the central government in Baghdad and Kurdish authorities in Arbil tussle over a disputed oil exploration deal with ExxonMobil and a row over energy contracts.

"Oil is still being illegally exported to Turkey," Shahristani said at a news conference in Baghdad, referring to Kurdish transportation of oil to Turkey in exchange for refined crude products.

Baghdad insists the central government retains the sole right to export crude and has threatened to sue companies that transport oil out of the three-province northern region.

Arbil, however, says it has the right to sign contracts independent of Baghdad's authority.

Shahristani also said Baghdad had transferred $540 million to Kurdistan to pay foreign energy companies working in the region, but claimed Arbil had not fulfilled its side of a September 2012 deal by upping exports.

Arbil, however, says it has slashed oil exports because Baghdad has not transferred all of the promised funds.

The two sides are at odds over issues including Kurdistan's refusal to seek central government approval for oil contracts it has awarded to foreign firms, and over a swathe of disputed territory in northern Iraq.

The central government regards all oil deals that did not go through the national oil ministry as illegal.