Iraq accused Kurdish peshmerga fighters of seizing two key northern oil fields near the disputed city of Kirkuk Friday, as relations between Baghdad and the autonomous Kurdistan region hit a new low.
"The oil ministry strongly condemns the seizure and control of crude oil (wells) in the Kirkuk and Bey Hassan oil fields this morning by groups of Kurdish peshmerga forces," the ministry said in a statement.
The two oil fields are said to have a combined daily output capacity of some 400,000 barrels per day, a ministry spokesman said.
Officials from the Kurdish regional government were not immediately available for comment.
The accusation marks an escalation in already-high tension between the Kurdish authorities and federal government, which has cast a pall over efforts to form a unity government to counter a raging Sunni militant insurgency.
Iraq's Kurds on Thursday said Prime Minister Nuri al-Maliki was "hysterical" and not fit to run the country, after he accused them of harbouring militants in territory they control.
"The oil ministry strongly warns the Kurdistan region of the danger of this irresponsible behaviour which violates the constitution and the national wealth, and disregards the federal authorities and threatens national unity," the statement said.
Iraqi lawmakers are due to meet on Sunday for a parliamentary session meant to revive flagging efforts to form a new government.
The only other time parliament has met since April polls ended with MPs exchanging heckles and others walking out.
Kurdish troops moved into disputed areas vacated by federal forces that failed to stop a Sunni militant onslaught that began on June 9.
The Kurds have since said those swathes of land were theirs to keep, and announced plans to hold a referendum on independence.