The outlawed Kurdish Workers' Party (PKK) launched a heavy attack on Turkish border posts that left 38 dead, Turkey's military leadership said Saturday in Ankara.

The PKK launched the attack from northern Iraq, the military said, which killed 15 Turkish soldiers and 23 PKK fighters. Some 20 Turkish soldiers were injured, and two soldiers were still unaccounted for.

The attack took place on the Aktutun border post in the south- eastern province of Hakkari.

Turkish Prime Minister Recep Tayyip Erdogan, who broke off a trip to Central Asia after hearing of the attack, said: "We will carry out our fight against terrorism with even more resolve."

The United States condemned the attack and called it a "vicious act of terrorism." A statement from the US State Department said, "We mourn this tragic loss with the citizens of Turkey."

"The United States considers the PKK a common enemy of Turkey, the United States and Iraq. We reiterate our longstanding call for the PKK to lay down its arms and cease its violence once and for all. We stand in solidarity with Turkey in our commitment to defeat these terrorists," State Department deputy spokesman Robert Wood said.

According to Turkish media reports, the border post was attacked by 350 PKK fighters using heavy weapons, leading to the high number of casualties on the Turkish side.

In the past, PKK fighters have abducted Turkish soldiers and taken them into Iraqi territory.

Turkish fighter jets have bombed suspected PKK bases in northern Iraq several times in recent weeks.

In February, the Turkish Army claimed to have killed 240 PKK fighters in a week-long ground offensive in Iraq. A total of 27 Turkish soldiers were killed in the offensive, which was restricted to the Kurdish Autonomous Region of northern Iraq.

The PKK is listed as a terrorist organization by the European Union and US. It has been fighting for independence or greater autonomy for the Kurdish parts of Turkey since the 1980s.

The Turkish Army says that at least 35,000 people have died in the fighting since then.