"The United States will continue our strong cooperation with the Turkish government as it works to defeat the terrorist threat from the PKK and to bring peace, stability and prosperity to all the people of southeast Turkey," Obama said.

The attacks by the separatist Kurdistan Workers' Party rebels occurred in eight locations in Cukurca and Yuksekova in Hakkari province near the Iraq border in the early hours of Wednesday, local security sources said.

Obama, who has established a close relationship with Turkish Prime Minister Recep Tayyip Erdogan, offered his condolences to the families of the victims of the violence and to the Turkish people.

"The United States strongly condemns this morning's outrageous terrorist attack against Turkey, one of our closest and strongest allies," he said in a written statement issued as he toured Virginia on a bus trip.

"The United States will continue our strong cooperation with the Turkish government as it works to defeat the terrorist threat from the PKK and to bring peace, stability and prosperity to all the people of southeast Turkey," he added.

"The people of Turkey, like people everywhere, deserve to live in peace, security and dignity. As they pursue the future they deserve, they will continue to have a friend and ally in the United States."

The PKK, which the US State Department has designated a foreign terrorist organization, has waged a 26-year separatist war in Turkey's Kurdish-majority southeast.

Washington has supplied Turkey, a NATO ally, with intelligence on PKK movements in neighboring northern Iraq, where the rebels take refuge, for use particularly in Turkish air raids on PKK hideouts.

The death toll in Turkey is the heaviest for the army since 1993, when the PKK killed 33 unarmed soldiers in southeastern Bingol province.

The group threatened Turkey with worse if the army follows through with a ground incursion into Iraq's autonomous north.