ISTANBUL — Fifteen Turkish soldiers were killed and at least 20 wounded in an attack by Kurdish separatist rebels in the mountainous border area of eastern Turkey, Turkish officials said Saturday.

The soldiers were killed Friday night in an attack on the Aktutun border post in Semdinli, a district that borders Iran and Iraq, the Turkish military said. Twenty-three Kurdish fighters of the Kurdistan Workers’ Party, also known as the P.K.K., were also killed.

The attack was the deadliest since last October, when Kurdish fighters killed 13 Turkish soldiers in an ambush near the town of Daglica. That attack touched off a political confrontation between Turkey and Iraq, where some rebels hide. Turkey bombed targets there, over Iraqi objections, and later sent troops in, but withdrew them eight days later under American pressure.

Turkey, a NATO member, has been fighting Kurdish separatists in its southeast since the 1980s. Kurdish rebels want greater autonomy for Turkey’s minority Kurdish population, a condition that Turkey says would lead to secession. The conflict has died down substantially since the bloody days of the 1980s and ’90s.

Even so, the attack was the most serious in a year, and the Turkish authorities will be under pressure to respond. Regional elections will be held in March, and Turkish officials will take pains to show the public that they are working hard to punish the rebels for their attacks.

Prime Minister Recep Tayyip Erdogan cut short a trip in Central Asia, and returned to Ankara, Turkey’s capital, where he spent more than two hours meeting with the country’s top security officials on how to respond to the attack. Though nothing specific was made public from the meeting, the Turkish president, Abdullah Gul, said in a statement that the attack would “be investigated until the very end to find out how and with whose help” it was carried out.

Brig. Gen. Metin Gurak of the Turkish General Staff told reporters in Ankara that the rebels had used heavy artillery, leading to the high number of military casualties, Turkey’s state-run Anatolian Agency reported. He said two soldiers were also reported missing after the attack.

General Gurak used language that appeared to hint that Turkey might be considering another military operation inside Iraq.

“Struggle with the separatist rebel organization will continue in and outside the country with increasing determination,” he said. “Nobody should have doubts about this.”

But it was too early to tell how Turkey would respond. Turkey often blames Iraq for harboring the fighters in its Kurdish enclave. But the P.K.K. has hide-outs in Turkey as well, and Iraqi officials say Turkey blames Iraq to avoid taking responsibility for rebels on its own soil.

In Baghdad, an Iraqi government spokesman, Ali al-Dabbagh, condemned the P.K.K. attack but called on Turkey to act with “wisdom and self-restraint,” Reuters reported. The Turkish Parliament is expected to approve a government request to extend a deadline that would allow the Turkish military to take action in northern Iraq. The current mandate expires Oct. 17.

Necati Ozgen, a retired general who has been in charge of the Aktutun base, said that assailants must have entered through Iraq, since the military base faces the small village right by the border and has unattainable high mountains behind it.

“There seems to be a major intelligence failure,” Mr. Ozgen said in an interview on Turkey’s NTV television. “It is impossible for a large group to reach as far as the base, before the villagers or village guards notice them.”

The border post, Aktutun Gendarmerie Station, has been attacked frequently in the past, most recently in May. NTV reported that 20 soldiers were killed in a major battle there in September 1992, when the war was deadlier.

Semdinli has also been the scene of violence in which the Turkish military has been incriminated. Several members of a paramilitary force are suspects in a bomb attack inside a bookstore in the largely Kurdish town in 2005. Turkey’s former top military commander, Yasar Buyukanit, acknowledged knowing one of the suspects, who had served under his command, describing him as a “good fellow.”

The men’s trial is still continuing, with the next hearing scheduled for Dec. 19.

Sebnem Arsu contributed reporting.

Copyright 2008 The New York Times Company