The Ankara crowd tried to set up barricades to cut off traffic, CNN reported.
Authorities in Istanbul said they were preparing for pro-government counter-demonstrations.
In May, demonstrators protested plans to level Gezi Park in Istanbul and build a mall. The protests mushroomed to demonstrations against the government of Prime Minister Recep Tayyip Erdogan.
CNN reported that police released 46 demonstrators who had been detained.
Anti-government protest organizers said Friday an overnight meeting with Erdogan led to a possible tentative agreement to end the civil unrest, The New York Times reported.
"We are going to discuss all of this with the people in Gezi Park and hear their say," Taksim Solidarity protest-group member Sami Yilmazturk said after meeting with Erdogan at his home in Ankara.
"We are not in a position to impose anything on [the thousands of Istanbul protesters], but we've reached our goal here," Yilmazturk said. "For the first time, the government responded to us positively."
The group and a spokesman for Erdogan's Justice and Development Party said the government agreed not to start construction in Gezi Park, in central Istanbul's Taksim Square, until a court rules if the work is legal.
If the court rules in favor of the government, the matter would be put to a referendum in Istanbul, the two sides said.
The late-night meeting with Erdogan came hours after the prime minister delivered a "final warning" to the thousands of defiant protesters encamped in the park, demanding they end their occupation.
Nationwide, four protesters and a police officer were reported killed in clashes since May 31. More than 5,000 protesters and 600 police officers were reported injured.