Turkish troops and Kurdish separatist rebels clashed on Thursday, in an upsurge of fighting the military said had killed five people on each side. A spokesman for the rebels based in Iraq said they had shot down a Turkish helicopter on the Turkish side of the border with Iraq on Wednesday. The Turkish military said it crashed because of technical failure, killing a soldier and wounding 15. Turkey's government and military are under increasing pressure to respond forcefully to Kurdistan Workers Party (PKK) guerrillas, who have stepped up deadly attacks against Turkish security forces in recent weeks. The General Staff said four soldiers died when PKK rebels opened fire on them in remote mountains in the province of Hakkari, near the border with Iraq. The helicopter, carrying reinforcements to the scene, crashed due for technical reasons, it said in a statement. Ahmed Danees, a PKK spokesman, told a Reuters correspondent in Kurdish northern Iraq by phone fierce clashes were continuing. “I can confirm to you that four Turkish soldiers were killed and a helicopter was downed by our fighters,” he said. It was not immediately possible to confirm either version. PKK rebels are known to have light anti-aircraft weapons. The PKK rebels were killed in operations in Semdinli and Sirnak near the Iraqi border, the General Staff said.