A rebel border attack near Turkey’s border with Iraq left 26 Turkish soldiers dead as Turkey retaliated with helicopter missile strikes.

Commandos were killed Wednesday by Kurdish militants after a group of Turkish soldiers went about 2 miles across the northern Iraq border in pursuit of rebels who attacked two districts in the Hakkari province, military sources told Al Jazeera.

Turkish forces responded with air strikes in the northern Iraqi mountains.

The Kurdistan Workers’ Party (PKK), which was been in an almost 30 year battle with the Turkish, told Al Jazeera Wednesday’s attack was in retaliation to a Turkish military campaign waged in June. At least nine Kurdish children were killed.

Kurdish rebels took arms against the Turkish state in 1984, in an attempt to establish an independent Kurdish homeland.

President Obama condemned the rebel attacks saying they were “outrageous.” The U.S. considers the PKK to be a terrorist group.

NATO Secretary General Anders Forgh Rasmussen issued a statement condemning the attacks, saying there was “no justification.”