Turkey has threatened to cross the Iraqi border to try to wipe out Kurdish rebel bases, arguing it has the right to fight terrorism. The United States and Iraq oppose such unilateral action, fearing it could destabilize northern Iraq, the most stable part of the country.
The protesters in Zakho waved the sunshine flag of Iraq's autonomous Kurdish region and accused Turkey of trying to foment unrest in the relatively peaceful autonomous region in northern Iraq.
Hussein Khalid, the mayor of Zakho, some 300 miles northwest of Baghdad, estimated the crowd size at about 15,000 people.
"This demonstration represents the angry of the Kurdish community toward the green light that was given to Turkish government by the parliament to invade Kurdistan," Khalid said in a telephone interview from another Kurdish city, Sulaimaniyah.
The protesters called on Turkey not to launch cross-border attacks against the rebels who operate from bases in the towering mountains inside Iraq.
"Our peaceful life here is threatened ... as war will bring us only problems and humanitarian crisis," said Jelveen Rikani, a 28-year-old government employee who took part in the demonstration. Turkey wants to turn the Kurdistan region into an unsecured and restive area just like the other parts of Iraq that are mired in chaos and blood."
The demonstrators waved the Kurdish flag, with a yellow sun against red, white and green stripes, and banners reading: "No, no to the Turkish military incursion. Yes, yes to peace and security," and "We will be a shield to defend our cities."
Protesters also took to the streets of Irbil and another border city Dahuk earlier this week, but Saturday appeared to be the largest demonstration following the Turkish parliament's vote on Wednesday giving a green light to the incursion. The Turkish government
PKK fighters operating from bases in the mountains of northern Iraq periodically cross the border to stage attacks in their war to win autonomy for Turkey's predominantly Kurdish southeast. More than 30,000 people have died in fighting that began in 1984.
Turkish leaders have said publicly that they would prefer a solution to the guerrilla problem that avoids a cross-border offensive, but Prime Minister Recep Tayyip Erdogan has warned that Turkey will take whatever steps it must to defeat the PKK.
Public anger is high in Turkey over a recent spate of guerrilla attacks in the southeast as well as a perception that the United States has failed to back Turkey in its fight with the PKK, even though Washington lists the movement as a terrorist group.
Meanwhile, the most senior leader in Iraq's Kurdish region appeared to raise the stakes in the standoff over northern Iraq on Friday, against any cross-border military strike on rebel bases.
The tough line taken by the Kurdish region's president, Massoud Barzani, further stoked worries that a Turkish incursion could ignite a wider cycle of conflict and unrest in one of the few stable corners of Iraq.
Barzani said urgent talks were needed on all sides. But Turkey has flatly declared it is out of patience with escalating attacks by separatist guerrillas who use hideouts in northern Iraq.
As both Baghdad and Washington struggled to avert conflict between two of its key allies in the region, Turkey's prime minister insisted that the camps of Kurdish rebels in northern Iraq must be destroyed and rebel leaders extradited to Turkey for trial.
Turkey's parliament on Wednesday gave the government a one-year window in which to launch cross-border offensives against Turkish Kurd rebel strongholds in Iraq. The vote led to large-scale protests by Iraqi Kurds, calls for restraint by Baghdad and Washington and uncertainty over Turkey's next move - which has helped push oil prices to record highs.