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 protests in Istanbul and several cities in the mostly Kurdish southeast, and were the latest incident of violence to undermine the 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 that 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, indicating 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 cannons to disperse pro-Kurdish demonstrators 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.