At least 55 Kurdish militants have been killed by Turkish warplanes in airstrikes that hit Kurdistan Workers Party (PKK) camps in northern Iraq.

Turkish security sources said the jets took off from a base in Diyarbakir, in Turkey's south-east.

Turkey's largely Kurdish south-east has been hit by almost daily fighting between PKK militants and security forces since the collapse of a ceasefire earlier this year.

Security forces responded by launching frequent bombing raids into mountainous northern Iraq where the PKK has camps.

It is the worst violence NATO member Turkey has seen in two decades, coinciding with fighting across the border in Syria involving government troops and Islamic State militants.

The PKK began its separatist insurgency in 1984, triggering a conflict that has killed more than 40,000 people.

The group, which said it is fighting for greater Kurdish autonomy, is listed as a terrorist organisation by Turkey, the European Union and the United States.

President Tayyip Erdogan promised the fight will go on until "not one terrorist is left".

The conflict has flared up as Turkey prepares for a parliamentary election on November 1 following an inconclusive June vote.

Reuters/AFP