The pro-Kurdish People's Democratic Party (HDP) said 126 of its buildings came under attack on Tuesday night by protesting nationalists.

The protesters - angered by the death of at least 31 members of Turkey's security forces killed by Kurdish rebel attacks - broke windows and set fire to the HDP's headquarters in Ankara.

"There are hundreds in front of the building now, chanting slogans and throwing stones, breaking the windows of our building. Police are just watching," Garo Paylan, an HDP lawmaker, told the Reuters news agency.

At least three people stuck inside the building during the attack were safely evacuated following police intervention.

"What's being broken there is our hope of living together," Paylan added.

The HDP made gains in June's elections, depriving President Recep Tayyip Erdogan's Freedom and Development Party (AKP) from gaining a parliamentary majority.

Separately, the headquarters of Hurriyet newspaper in Istanbul was pelted with stones by a group of a hundred people for the second time in three nights, the daily said.

'Unacceptable'

Turkish Prime Minister Ahmet Davutoglu denounced the attacks via Twitter, calling the crowd violence "unacceptable."

"It is unacceptable to damage media institutions, political party buildings and the property of our civilian citizens," Davutoglu said.

"I invite all my citizens with heart full of love for the country to calm, embrace on another, and to have confidence in the state."

Violent escalation

On Tuesday, Ankara launched an aerial and ground assault on PKK targets in northern Iraq, marking the first incursion into Turkey's neighboring country to fight Kurdish rebels since 2011.

A series of attacks on both sides of the conflict erupted in July, undermining a fragile peace initiative between the Turkish government and Kurdish rebels launched in 2012 by Erdogan.

The Kurdish insurgency for independence has spanned three decades and left more than 40,000 people dead.

ls/jr (Reuters, AP, dpa)