The Turkish foreign ministry said it communicated "in the strongest possible terms" to US Ambassador David Satterfield Ankara's displeasure with Washington's refusal to immediately accept Turkey's version of events.

The Kurdistan Workers' Party (PKK) blamed the deaths on Turkish forces, which launched an operation last week against its militant hideouts in the mountainous regions of northern Iraq.

The US State Department on Sunday published the following statement: "If reports of the death of Turkish civilians at the hands of the PKK, a designated terrorist organisation, are confirmed, we condemn this action in the strongest possible terms."

A Turkish diplomatic source told AFP that Ankara was unhappy with the US statement because it appeared to express doubt in Turkey's version of events.

President Recep Tayyip Erdogan called Washington's statement a "farce".

The United States and Turkey's other Western allies recognise the PKK as a terror group.

But Washington work in Syria with another Kurdish militia that Turkey views as a branch of the PKK.