ANKARA, Turkey - Turkish warplanes mistakenly killed 35 smugglers and other villagers in an operation targeting Kurdish rebels in Iraq, a senior official said Thursday, one of the largest one-day civilian death tolls during Turkey's 27-year drive against the guerrillas.

The killings spurred angry demonstrations in Istanbul and several cities in the mostly Kurdish southeast, and were the latest incident of violence to undermine the Turkish government's efforts to appease the aggrieved Kurdish minority by granting it more cultural freedoms.

Huseyin Celik, a spokesman for Prime Minister Recep Tayyip Erdogan's ruling party, said authorities were still trying to identify the dead, but that most were youngsters from an extended family in the mostly Kurdish-populated area that borders Iraq.

All of the victims were under age 30 and some were the sons of village guards who have aided Turkish troops in their fight against rebels, he said.

"According to the initial information, these people were not terrorists but were engaged in smuggling," Celik said, adding that Turkey was ready to compensate the victims. "If there was a mistake, if there was a fault, this will not be covered up, and whatever is necessary will be done."

In Istanbul, police used tear gas and water canons to disperse pro-Kurdish protesters denouncing the air strikes, the Dogan news agency reported. Dogan footage showed some demonstrators smashing glass panels at a bus stop and others throwing stones at a police vehicle near Taksim square, a transit hub adjacent to shopping and hotel districts. Plainclothes officers hustled or dragged away several protesters.

Earlier, the Turkish military confirmed the Wednesday night raids, saying its jets struck an area of northern Iraq frequently used by rebels to enter Turkey after drones detected a group approaching the often unmarked mountainous border. Border troops were on alert following intelligence indicating that Kurdish rebels were preparing attacks in retaliation for recent military assaults on the guerrillas.

The military said drones had detected a group approaching Turkey, apparently at a mountain pass that the rebels have used to smuggle weapons into Turkey, and that the military conducted strikes in areas where the rebels have bases far away from civilian settlements.

Pro-Kurdish legislator Nazmi Gur said earlier that most of those killed were teenagers making a living out of smuggling from Iraq into Turkey and claimed that officials should have known that Turkish smugglers would be operating in the area.

Video footage provided by Dogan on Thursday morning showed mourners, some crying, as they surrounded more than a dozen bodies that lay side-by-side and wrapped in blankets in the Turkish village of Ortasu.

Ahmet Deniz, a spokesman for the rebel group, said earlier that the victims were among a group of about 50 people attacked on their way back to Turkey from Iraq's self-ruled northern Kurdish region. Most of the survivors were injured, he said.

"Those who were killed yesterday had no links to the PKK. They were only smugglers who were on their way back to Turkey from Iraq," Deniz said, referring to the Kurdish rebel group, the Kurdistan Workers' Party.

"We were on our way back when the jets began to bomb us," the pro-Kurdish Firat news agency quoted one survivor, Servet Encu, as saying. "Five or six took refuge behind some rocks, but the planes bombed those as well. They all died behind the rocks."

Firat said some of the survivors rushed back to Ortasu for help and that its villagers then transported the bodies back to the village. Some of the bodies were carried to the village tied to donkeys or to mules, photographs obtained by The Associated Press showed.

Gur's pro-Kurdish party released a statement condemning "the massacre," and Turkey's main opposition party said it was "extremely disturbed" that civilians were apparently killed in the fight against the PKK.

Hundreds of Kurds staged a protest in the town of Yuksekova, in Sirnak province, to denounce the raids and call for the resignation of Turkey's interior minister, Dogan reported. Police used tear gas and water canons to disperse the group, and some retaliated by throwing stones, the agency said.

Kurds, who make up around 20 percent of Turkey's 74 million people, have long felt marginalized in the country and many want autonomy in Kurdish-dominated southeast Turkey. Since Kurdish rebels took up arms in 1984, tens of thousands of people have been killed in the conflict with the state.

The rebels have long used northern Iraq as a springboard for hit-and-run attacks on Turkish targets. This year, Turkey's air force has launched dozens of air raids on suspected rebel bases and other targets in northern Iraq and along the Turkish side of the mountainous border.

Turkish authorities said at least 48 suspected rebels were killed in two offensives backed by air power in southeast Turkey last week.

The government also has taken steps toward improving the standing of Kurds, including by allowing Kurdish-language institutes and private Kurdish courses as well as Kurdish television broadcasts. But it won't permit lower-level education in Kurdish.

The European Union, which Turkey is striving to join, has pushed the Turkish government to grant more rights to the Kurds. But EU countries also have urged Kurdish lawmakers to distance themselves from the PKK, which is considered a terrorist group by the United States and the EU.