The demonstration had ended peacefully, but a group of Kurdish youths embarked on a march, hurling petrol bombs and stones at shops, apartment buildings and cars.
The Kurdish you were confronted by a group of Turkish nationalists who were reportedly armed with knives and sticks, and several with guns.
Gunshots were heard as the two groups attacked each other before riot police arrived, firing tear gas to disperse the crowd.
Protestors also took their frustration over the ruling in Diyarbakir, the largest city of the Kurdish-majority southeast, hurling stones and fireworks at security forces who responded with pepper gas and water cannon.
Several people were reportedly injured in the clashes.
Paramilitary soldiers were also called in to help the police in the town of Yuksekova, where protestors set barricades in the streets, officials said.
At least 15 people were detained in the two demonstrations.
In Hakkari, the authorities said they captured a demonstrator who had snatched a policeman's gun in street clashes on Saturday.
DTP's closure came atop already simmering tensions after Kurdish fighters killed seven soldiers in an ambush in northern Turkey on Monday.
The fighters said the attack was a reprisal for the prison conditions of Abdullah Ocalan, their jailed leader, which Kurdish activists claim have deteriorated, and the killing of a Kurdish student in demonstrations last week.
The mounting violence has overshadowed government plans announced in August to expand Kurdish freedoms in a bid to erode popular support for the rebels and end the conflict in the southeast, which has claimed some 45,000 lives.