Baghdad's oil ministry condemned Iraqi Kurdistan Saturday for further exports of crude from wells in the autonomous northern region, part of a long-running row over the country's vast hydrocarbon reserves.

The federal government alleged that a shipment of oil, the second to be pumped in the three-province Kurdish region and shipped internationally in the past month, had been sent to Israel. It reiterated the threat of legal action against any companies that receive the crude.

"The oil ministry strongly condemns the Kurdistan region government's continued export of Iraqi oil from the region's fields... in flagrant violation of the values and principles" of the country, the statement said.

"The ministry is continuing to follow and pursue the shipments."

It said it had taken a series of measures to deter buyers, including "warning all companies and oil markets against dealing with these shipments, which have been taken out (of Iraq) illegally."

The statement is the latest salvo in a years-long dispute between the two sides over oil extracted in the autonomous Kurdish region.

The dispute centres on interpretations of Iraq's constitution, with each side insisting it is behaving legally.

The federal government insists it has the sole right to export Iraqi crude and says contracts between Kurdish authorities and foreign energy firms without its expressed consent are illegal. The regional government in Arbil rejects that.

The row has taken on a new dimension in recent days, with a major militant offensive that has overrun swathes of the country and swept federal forces aside, allowing Kurdistan to impose de facto control over disputed northern territory.