Tear gas fired into a crowd of demonstrators caused a disabled woman to fall out of her wheelchair outside a courthouse in Ankara.
Around 2,000 people gathered to protest against the handling of the trial of a policeman accused of killing a demonstrator earlier this year.
A group of protesters wielding sticks descended on the court entrance after a ruling that the accused officer could take part in court hearings via video link, prompting police to intervene, according to a witness.
Several protesters were wounded and 18 detained, according to local media reports. Ankara police declined to confirm the arrests and the crowd was later dispersed.
Officer Ahmet Sahbaz is accused of killing Ethem Sarisuluk, shot dead in June during a wave of nationwide anti-government demonstrations set off by a tough police response to a protest over the redevelopment of a park in Istanbul.
Six people, including a police officer, died during the weeks of unrest, which presented one of the biggest challenges to Prime Minister Tayyip Erdogan's decade-old rule.
Demonstrators, some armed with rocks, fireworks and petrol bombs, fought police firing tear gas, water cannon and pepper spray night after night, with the worst of the violence in Istanbul and Ankara.
Amnesty International said this month Turkish authorities committed widespread rights abuses during the unrest, beating and harassing protesters. Turkish officials have defended the police response and said such abuses will be investigated.
The hearing was adjourned to Dec. 2, media reports said.