Turkish Prime Minister Recep Tayyip Erdogan says calm is returning to his country, while he dismissed anti-government protests as bitterness over lost elections.
Thousands have marched in Ankara and other cities since Friday, accusing the prime minister of imposing Islamic views on a secular nation.
At least one person has been killed so far and hundreds injured as police used tear gas and water cannons against rock-throwing crowds.
Mr. Erdogan is showing no signs that he is willing to compromise. He says the protesters are walking arm-in-arm with terrorists and that they have no support among most Turks.
Turkish President Abdullah Gul is urging Turks to stay calm, but he defended their right to protest.
In Washington, White House spokesman Jay Carney said the United States is seriously concerned about reports of excessive force by police, and he urged all sides to avoid violence. He said the right to peaceful protest is fundamental to any democracy.
The protests began Friday as a demonstration against plans to dig up a park in Ankara for a new mosque. But some of the marchers say they are very angry at Mr. Erdogan's conservative Islamic-oriented government and what they see as its interference in the lives of citizens who do not share his religious views.
US SECRETARY OF STATE JOHN KERRY:
"The United States supports full freedom of expression and assembly including the right of people to peaceful protest, because that is fundamental to any democracy. And we are concerned by the reports of excessive use of force by police. We obviously hope that there will a full investigation of those incidents and full restraint from the police force with respect to those kinds of incidents. And we urge all people involved - those demonstrating and expressing their freedom of expression and those in the government - to avoid any provocation of violence."