Iraq's Oil Ministry has criticised the autonomous Kurdish region for its move to sell oil independently, saying it was a violation of the constitution and amounts to smuggling.
Friday's strongly worded statement came after the Kurdish regional government announced that its first shipment of crude oil exported directly to Turkey had gone on sale, with more expected to follow.
It is just the latest chapter in a long-running tussle between the federal government and the Kurdistan region over natural resources.
The three-province region's plan to sell oil it has exported to Turkey "is considered ... an explicit violation of the requisites of the Iraqi constitution", the Oil Ministry said in an English-language statement.
The federal State Oil Marketing Organisation "is the exclusive, sole official body authorised to enter into contracts for the export of hydrocarbon resources, including crude oil and gas", the statementt said.
Any other exports are "considered as 'smuggled crude' and in violation of the valid laws", it said, also criticising Turkey for facilitating the move by Kurdistan.
The Kurdish region earlier this week issued a statement giving "public notice of the commencement of the sale of its first shipment of crude oil exported via [the] Kurdistan region's new pipeline through Turkey to the port of Ceyhan".
The sale of the first two million barrels of crude was expected by the end of this month, with more to follow, the statement on the region's website said.