The protesters gathered in the city centre in support of an Ankara academic and a teacher on hunger strike.
The protesters gathered in the city centre in support of an Ankara academic and a teacher on hunger strike for more than four months to protest against their sacking.
As well as tear gas, police also used water cannon to break up the protest.
Police arrested more than 40 people, the CNN-Turk and NTV television stations reported. One of those arrested said he had had his arm broken while resisting, the AFP journalist at the scene reported.
Academic Nuriye Gulmen and teacher Semih Ozakca were fired by a government decree under the state of emergency imposed after the July 15 coup bid last year.
They started their hunger strike after demonstrating for 100 days to dispute their sacking.
In May, they were both detained and accused of belonging to a banned far-left group. Prosecutors want them jailed for 20 years.
Their case has been taken up by rights activists, who accuse the government of using last year's coup bid as a pretext for cracking down on all critical voices.
On Friday, Council of Europe secretary general Thorbjorn Jagland expressed his "deep concerns" for the two hunger strikers and called for their release.
In the wake of the failed coup bid, authorities embarked on the biggest purge in Turkey's history, arresting 50,000 people and sacking almost three times that number. They include judges, teachers, doctors and members of the armed forces.