Speaking to a press conference in Istanbul, Erdogan said the referendum was null and void to Turkey.
“Regardless of the results, the referendum, which is not in conformity with the current law in Iraq, is null and void for us, we call it illegitimate,” Erdogan said.
He reiterated Turkey’s support for Iraq’s territorial integrity and social unity, adding, “And we will work to ensure that.”
“We are taking all kind of steps in northern Iraq, particularity on political, economic, commercial and security issues,” he said.
He pointed to the ongoing military drill at Turkey's border with northern Iraq, adding that more measures would be announced soon.
“At the same time, the [Turkish] Air Force is in the same situation and only permits passage as far as the Iraqi border," he said.
"We will immediately announce other measures and steps taken this week.”
‘We hold the valve, we can shut it’
Erdogan also underlined that the border crossing to and from northern Iraq would be blocked.
"Let’s see how and where the northern Iraq local authority sells petroleum," he said, adding that Turkey is the only way for northern Iraq’s oil to reach world markets.
“The [oil] valve is ours. If we shut off the valve, it will be over.”
He said the KRG must step back from its referendum decision otherwise “we will continue to take steps with determination."
Monday's non-binding referendum will see voters in northern Iraqi Kurdish Regional Government (KRG)-held areas, including areas disputed between Erbil and Baghdad, vote on seceding from Iraq.
Baghdad, Turkey, Iran, the U.S., and the UN have all spoken out against the poll, saying it will only distract from the ongoing fight against Daesh and further destabilize the region.
Iraq’s central government has threatened to intervene militarily if the vote leads to violence.
KRG President Massoud Barzani has said a “Yes” win would not result in an automatic declaration of independence but would simply lead to further negotiations with Baghdad.
EU accession talks
On Turkey's European Union accession talks, Erdogan said that the EU process had turned into a “theater play.”
“The side which needs to decide on this issue [whether to suspend accession talks] and declare it to the whole world is the European Union,” he said.
“Let them make their decision. We will make the decision comfortably. They need not worry,” he said.
“We will wait patiently until we hear this decision.”
After tension rose between Turkey and some EU states following last year's defeated coup attempt, some politicians, particularly in Germany, publicly proposed halting accession talks amid a non-binding European Parliament vote on shelving discussions.
The European Council will discuss Turkey's negotiations next month, although some member states like Hungary, Finland, Lithuania, and Ireland have openly opposed German proposals to suspend talks.
Turkey has already fulfilled the EU’s full membership requirements, Erdogan said.
“With regards to chapters and legislative alignment, we do not have any shortages or problems. We only face a problem that the European Union isn’t fulfilling its own responsibilities,” he said.
The EU destroyed its reputation by failing to keep its word on its responsibilities such as refugees, he added.
Turkey’s EU accession talks began in 2005. To gain membership, Turkey has to successfully conclude negotiations with the EU in 35 policy chapters that involve reforms and the adoption of European standards.
Negotiations hit a stalemate in 2007 over the Cyprus issue. The German and French governments have also opposed the country’s full EU membership.
Violent persecution of Rohingya
Erdogan criticized the international community for failing to take sanctions on Myanmar to prevent violence against the country’s Rohingya Muslims.
“Myanmar is now seeing an altogether ‘Buddhist terror’,” he said. “They may rebuke Erdogan [over his remarks]. They are free to do so.”
“There is a clear fact. All of humanity should know this,” Erdogan added.
Since Aug. 25, more than 429,000 Rohingya have crossed from Myanmar's western state of Rakhine into Bangladesh, according to the UN's migration agency.
The refugees are fleeing a fresh security operation in which security forces and Buddhist mobs have killed men, women and children, looted homes and torched Rohingya villages.
According to Bangladeshi Foreign Minister Abul Hasan Mahmood Ali, around 3,000 Rohingya have been killed in the crackdown.
The Rohingya, described by the UN as the world's most persecuted people, have faced heightened fears of attack since dozens were killed in communal violence in 2012.