Dozens of nationalist protesters yesterday marched on the the headquarters of the pro-Kurdish Peoples' Democratic Party (HDP) in Ankara, throwing stones and ripping down the sign outside, pictures broadcast by the CNN-Turk channel showed.
"Our headquarters in under attack but the police is not performing its duties," the party said on its official Twitter feed.
Smoke was seen coming from the building, an AFP photographer said, although police eventually dispersed the demonstrators.
Pictures posted on social media suggested the interior of the building had been badly damaged in the attack with some offices completely gutted by fire.
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In the southern resort city of Alanya, the local HDP headquarters was set on fire, sending yellow flames into the night sky, CNN-Turk reported.
Reports said 2,000 people carrying the Turkish flag had marched on the building, with the fire eventually doused by the fire brigade.
Similar nationalist demonstrations were taking place across Turkey, with protesters damaging HDP buildings in at least six other cities, it said.
The violence against the HDP also came as the headquarters of Turkish newspaper Hurriyet in Istanbul were attacked for the second time in three nights.
Windows were smashed and the building pelted with stones until the riot police finally arrived, the paper said.
In a series of tweets urging calm, Prime Minister Ahmet Davutoglu condemned the damage inflicted on newspapers and political party headquarters as "unacceptable".
"No-one should put themselves above the law," he said.