The referendum on independence for Iraqi Kurdistan is now "a thing of the past", Iraq's Prime Minister Haider al-Abadi said Tuesday.

Baghdad responded to the September poll, in which Kurds overwhelmingly voted for independence, with a military operation this week to retake disputed parts of oil-rich Kirkuk province.

"Central authority must be imposed everywhere in Iraq," Abadi told a press conference. "I want to be fair with all citizens."