Turkey has vowed to crush a Syrian Kurdish militia called the People's Protection Units (YPG), which it considers a terrorist group.

Turkish President Recep Tayyip Erdogan says it is an extension of the banned Kurdistan Workers' Party, which has fought for Kurdish autonomy in Turkey for three decades.

The YPG denies any direct organisational links - an assertion backed by a US-led coalition whose air strikes have helped the militia and allied Arab fighters drive Islamic State militants from tens of thousands of square kilometres of Syria.