As Iraqi Kurds are preparing to launch an independence referendum, despite Baghdad’s objections and international calls to postpone the vote, neighboring countries are holding massive wargames on territories adjacent to the Kurdish-held areas.

Iran’s Revolutionary Guards Corps (IRGC) has launched military drills, codenamed “Muharram,” on Saturday, Sepah News agency, IRGC’s media arm reported. The drills take place in the northeastern West Azerbaijan province, bordering Iraqi Kurdistan, and feature armored units, artillery pieces and aircraft.

The first day of the exercise focused on training night operations, live artillery fire as well as search and destroy border operations, according to an IRGC spokesman.

While the war games are a part of annual events, marking the start of the Iranian-Iraqi war in 1980, according to Iranian state media, they started just a day before the independence referendum. Kurdish news outlets have reported a number of stray artillery shells landing in Iraqi territory.

In a separate development, Iran has halted all flights to Iraqi Kurdistan in the wake of the Kurdish “insistence on holding the referendum.”

“All the flights from Iran to Sulaimania and Erbil airports, as well as flights through our country’s airspace to the Kurdish regions have been suspended under a request from the central Iraqi government,” Fars news agency cited the press secretary for Iran’s supreme national security council, Keyvan Khosravi, as saying.

READ MORE: As Kirkuk boils, Kurdistan about to hurl Iraq into turmoil over ‘independence’ referendum

Tehran earlier warned the Kurdish Regional Government (KRG) that holding the referendum and breaking from Iraq would result in the border being closed and the annulling of all the agreements with the region.

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Meanwhile, Turkey has been holding massive military drills with around 100 military vehicles, including tanks and howitzers, exercising on the Iraqi border since Monday.

The wargames entered a “second phase” on Saturday, as additional troops poured in to participate. The Turkish parliament on Saturday also voted to extend the mandate of its troops in Syria and Iraq by another year.

The Turkish Air Force targeted the positions of Kurdistan Workers Party (PKK) in northern Iraq on Sunday. The strikes destroyed artillery positions, caves and other facilities used by the militant group. Turkey frequently carries out such operations against the PKK, which is designated by Ankara, Washington and a number of other countries as a terrorist group.

The upcoming referendum is opposed not only by the central Iraqi government, Iran and Turkey, which have large Kurdish minorities of their own, but also the international community, which fears that the move can result in further destabilization of the region.

UN Security Council has voiced concern over the “potentially destabilizing impact” of the referendum on Thursday, as it “could detract from efforts to ensure the safe, voluntary return of over three million refugees and internally displaced persons.”

Earlier this week, UN Secretary-General António Guterres has voiced similar concerns, urging all the parties to obtain from destabilizing actions.

“The Secretary-General calls upon the leaders across Iraq to approach this matter with patience and restraint. The United Nations stands ready to support such efforts,” Guterres said.

The US, which has pledged support for Kurds in Iraq for years allying with them in the fight against Islamic State (IS, formerly ISIS/ISIL), now says it “strongly opposes” the referendum. A security warning was issued on Sunday ahead of the referendum, urging US citizens to abstain from traveling “into and within territories disputed between the Kurdish Regional Government and the Government of Iraq” as there might be “unrest” during the polls.

“US Embassy Baghdad cautions US citizens in Iraq that there may be unrest if the Kurdistan Regional government carries out an independence referendum on September 25,” the US Embassy in Baghdad said in a statement.