An angry Erdogan told reporters at Istanbul airport as he headed for Saudi Arabia on Tuesday that Demirtas' remarks made in a meeting of Kurdish groups on Sunday amounted to "clear provocation."

"A certain leader … talked nonsense and what he did is a clear provocation and treason," said Erdogan, referring to Demirtas, who heads the pro-Kurdish Peoples' Democratic Party (HDP).

"How dare you talk about establishing a state in the south-east and the east within Turkey's existing unitary structure?" Erdogan said, and warned that the HDP would be "taught a lesson by our citizens and the law."

Referring to the PKK, Erdogan accused HDP politicians of being "puppets of the terrorist organization."

Demirtas facing prosecution

Prosecutors on Monday opened a criminal investigation against Demirtas, who heads the HDP with co-chairwoman Figen Yuksekdag and has become Erdogan's key rival over the last year.

It also emerged Tuesday that Prime Minister Ahmet Davutoglu had cancelled a meeting due this week with Demirtas to discuss constitutional reforms.

Participants at the two-day congress in the mainly Kurdish city of Diyarbakir had called for more self-governance.

Scores killed, curfews

Tensions are high in Turkey's southeast, where the Turkish military has pressed attacks in recent weeks against alleged members of the militant Kurdistan Workers' Party (PKK).

The army has said 210 militants have been killed. Curfews have been applied in provinces such as Sirnas.

The HDP has said a total of 129 civilians have been killed in towns under curfew since 16 August, and dozens injured.

Local media reported this week that a 5-year-old boy was shot dead while playing in the garden of his home in the flashpoint town of Cizre.

"A bullet fired from a Kalashnikov rifle hit the back of his neck," said the newspaper Hurriyet, which added that officials had denied that any security operation had taken place in the adjacent street.

The army has barred access to outside observers, making it impossible for journalists to verify the figures given.

The violence has flared since the collapse of a ceasefire in July.

Magazine journalists freed pending trial

In a parallel development Tuesday, the news agency AFP said a Turkish court had released two journalists pending trial.

Cevheri Guven and Murat Capan face charges of plotting a coup because of a magazine cover criticizing Eredogan's November re-election.

The private Dogan news agency said the pair was released pending trial on charges that could carry jail terms of up to 20 years. They were arrested after Erdogan's Justice and Development Party (AKP) swept to an unexpected win in November.

An Istanbul court later ordered the magazine Nokta be withdrawn from shelves.

ipj/jil (AFP, Reuters, dpa)