Clashes were reported near Istanbul on Monday during the high-profile trial of 275 people accused of attempting to overthrow government, according to BBC News.
Thousands of demonstrators gathered at the prison complex in the Istanbul suburb of Silivri to support hundreds of detainees charged in the so-called "Ergenekon" plot, according to Agence-France Press.
Monday's Silivri rally drew as many as 10,000 people angered by the four-year case, believing it to be politically motivated, said AFP. The government accuses the group of attempting to overthrow the ruling pro-Islamic Justice and Development Party (AKP).
CNNTurk reported one demonstrator suffering a heart attack during the upheaval, but said it was not fatal, according to AFP.
Some demonstrators attempted to break through police blockades in front of the courthouse, said BBC.
The trial is controversial because Prime Minister Recep Tayyip Erdogan's administration has arrested hundreds of military personnel since he took office in 2003, a position he won a year after AKP came to power, said AFP.
Among those accused are prominent lawyers, professors and reporters, and some in the group face a potential life sentence, said AFP.
A final verdict will reportedly be issued within the next few weeks.