HARARE, Zimbabwe — The Zimbabwean police on Friday violently extinguished a protest against President Robert Mugabe in the capital, Harare, cracking down on a united show of force by Zimbabwe’s political opposition.

Despite a last-minute court order allowing the demonstration to proceed, the police used tear gas and water cannons to disperse a crowd of hundreds from a square in Harare, beating protesters with batons.

Mr. Mugabe’s government has been challenged by a series of public protests in the past two months, fueled by widespread anger over the deteriorating economy. But the broad array of opposition figures and the swiftness of the police reaction, despite the court order, signaled a new level of tension.

Leaders of an emerging coalition against Mr. Mugabe — including Morgan Tsvangirai, the nation’s longtime opposition figure, and Joice Mujuru, a former vice president who broke with Mr. Mugabe — were chased from the square by the police and fled in their cars.