Iraq's oil ministry said on Sunday the agreement Germany's RWE signed with the Kurdish Regional Government, which included possible future gas supply for the Nabucco pipeline project, is illegal.
"The export of crude oil, gas and their derivatives are exclusively under the authority of the Oil Ministry of the central government in Baghdad and State Oil Marketing Organisation (SOMO)," oil ministry spokesman Asim Jihad said, reading a statement from the ministry.
On Friday, Germany's RWE said it had signed a gas co-operation agreement with Iraq's Kurdish regional government.
The deal envisaged RWE helping develop and design domestic and export gas transport infrastructure and create a route to market for Iraqi Kurdistan's gas.