The clashes, which Gul said took place on Sunday, would be the first known armed confrontation between US forces and members of the separatist Kurdistan Workers' Party (PKK) since the United States occupied Iraq.

However, a spokeswoman for the US military in Baghdad told Aljazeera.net on Monday it had no information regarding the clash. She said the US army was investigating the matter.

"Not only US soldiers, but also peshmergas clashed with the PKK," Gul said on Monday in reference to fighters from Kurdish groups in northern Iraq who are allied with Washington.

"Several American helicopters were also involved," AFP quoted him as saying.

Turkey has repeatedly called on the US to move against the PKK guerrillas, who have set up bases in a mountainous region of northeastern Iraq.

Action plan

Ankara had recently expressed frustration over what it saw as US reluctance to purge northern Iraq of the PKK, branded a "terrorist" organisation by both countries.

But last month, the two sides agreed on an "action plan", including military measures, against the group.

Ankara says up to 5000 PKK rebels are hiding in the mountains of northern Iraq.

In September, the PKK, which fought a bloody 15-year campaign for self-rule in predominantly Kurdish southeast Turkey, ended a four-year unilateral ceasefire with the Ankara government.