Turkish police have clashed with hundreds of supporters of a pro-Kurdish party in the south-eastern city of Van.
Tear gas was used to break up the rally by the Democratic Society Party when activists chanted in favour of jailed Kurdish rebel leader Abdullah Ocalan.
On Friday, prosecutors opened a case aimed at banning the DTP, which has 20 seats in the 550-member parliament.
Prosecutors allege the party is linked to the banned Kurdistan Workers' Party (PKK). The DTP denies any such claim.
The legal action comes amid tensions with Iraq over Turkey's threat to make cross-border attacks on PKK bases.
Turkey has recently massed about 100,000 troops on the Iraqi border after its parliament approved calls for a military incursion to deal with the insurgents.
Police fired warning shots and used tear gas to disperse the rally, during which several DTP supporters were also arrested, according to local media reports.
The DTP has called on Ankara to grant greater autonomy to Turkey's mainly Kurdish south-east.
Abdullah Ocalan was captured in 1999 and sentenced to life in jail
Party leaders insist they support a united Turkey and an end to violent conflict, and deny any links to the PKK, which is designated a terrorist group by Turkey, the US and the EU.
The PKK has waged a violent campaign for Kurdish autonomy since 1984, resulting in more than 37,000 deaths. It claims to fight for political and cultural rights for ethnic Kurds.
Abdullah Ocalan was captured in 1999 and is serving a life sentence after he was found guilty of treason for leading the Kurdish armed campaign.
A lull in fighting lasted until two years ago, when the clashes resumed. Earlier this year they intensified.