Turkish President Recep Tayyip Erdogan on Tuesday accused the leader of the main Kurdish party Selahattin Demirtas of "treason" over his call for autonomy for the country’s Kurdish minority.

Turkish President Recep Tayyip Erdogan on Tuesday accused the leader of the main Kurdish party Selahattin Demirtas of "treason" over his call for autonomy for the country's Kurdish minority.

In a speech at the weekend, Peoples' Democratic Party (HDP) co-chairman Demirtas said that Turkey's largest ethnic minority had to decide whether to live in autonomy or "under one man's tyranny".

On Monday, prosecutors opened a criminal investigation against him for crimes against the constitutional order over suggesting Kurds should push for autonomy in their stronghold of the southeast of the country.

"What the co-leader has done is clearly provocation, treason," Erdogan told reporters Tuesday at Istanbul airport before leaving for Saudi Arabia.

"This is the time when the masks have been taken off and the real faces exposed," he said.

The charismatic 42-year-old Demirtas has emerged as Erdogan's key rival over the last year, with many commentators saying he is the only politician to rival the Turkish strongman's rhetorical skills.

Under party rules Demirtas shares the leadership of the HDP with a woman, Figen Yuksekdag.

In an address to HDP lawmakers in the parliament, Yuksekdag hit back, saying: "If there is a word to describe us, it's not treacherous but loyal. We are loyal to our peoples' struggle."