Turkish troops dug in on the country's southern border on Tuesday and turned their weapons towards Kurdish-run northern Iraq, where authorities plan an independence referendum in defiance of Ankara and Western powers.
Tanks and rocket launchers mounted on armoured vehicles faced the Iraqi frontier, about 2 km (one mile) away, and mechanical diggers tore up agricultural fields for the army to set up positions in the flat, dry farmlands.
The military drill, launched without warning on Monday, is due to last until Sept. 26, Turkish military sources said, a day after the planned referendum for Kurdish independence in northern Iraq.
A Reuters reporter saw four armoured vehicles carrying heavy weaponry and soldiers taking positions in specially dug areas, their weapons directed across the border. A generator and satellite dish could be seen at one location.
The show of force reflects the scale of concern in Turkey, which has the largest Kurdish population in the region, that the vote could embolden the outlawed Kurdish PKK which has waged a three-decade insurgency in Turkey's southeast.
Foreign Minister Mevlut Cavusoglu said last week Ankara would not shy away from using force if necessary, and the showdown has hit the Turkish lira. It weakened beyond 3.5 to the dollar on Tuesday for the first time in four weeks.
Turkey has long seen itself as protector of the ethnic Turkmen minority, with particular concern about the oil city of Kirkuk where Kurds have extended their control since seizing the city when Islamic State overwhelmed Iraqi forces in 2014.
Tensions spread to Turkish markets.
"The increasing tension before the referendum in northern Iraq continues to effect lira negatively," Kapital FX Research Assistant Manager Enver Erkan said.
Cross-border trade, however, appeared to continue. Despite the nearby military manoeuvres a kilometre-long line of traffic, mostly trucks and cargo, queued to enter Iraq at the Habour border gate.
Turkey's strong economic ties to the Kurdish Regional Government (KRG) will weigh on any response from Ankara. The KRG pumps hundreds of thousands of barrels of oil per day and has approved plans for Russian oil major Rosnef to invest in pipelines to export gas to Turkey and Europe.
The military exercises came as Turkey, the central government in Baghdad and their shared neighbour Iran all stepped up protests and warnings about the independence referendum in the semi-autonomous Kurdish northern Iraq.
The United States and other Western countries have also voiced concerns and asked Iraqi Kurdish leader Massoud Barzani to call off the vote, citing fears the referendum could distract attention from the fight against Islamic State (IS) militants.
Iraq's Supreme Federal Court ordered Barzani to suspend the vote and approved Iraqi Prime Minister Haider al-Abadi's demand to consider "the breakaway of any region or province from Iraq as unconstitutional", his office said on Monday.
Turkey has brought forward to Friday a cabinet meeting and a session of its national security council to consider possible action.