The government’s chief spokesman said the demonstration was banned and that police acted in response to what he described as provocative behaviour by the protesters.
Activists have been staging protests around the country since February, inspired by uprisings elsewhere in the Arab world. But in the past few weeks security forces have taken a tougher line and started dispersing the demonstrations.
Mounaim Ouihi, one of the organisers of Sunday’s protest, said 15,000 people gathered in the Sbata district of Casablanca to demand more democratic freedoms, jobs and better social conditions.
He said police blocked streets around the area to prevent more people joining, and then sent 30-strong squads of truncheon-wielding officers charging into the crowd from various directions to disperse the protest.
“There was a lot of violence, and we are now calling a halt,” said Ouihi. “This protest has again sent out our message demanding freedom.”
“The government says it has financial problems and so cannot satisfy our demands, but you don’t need a budget for liberty.”
In much of the Sbata district, life went on unaffected and shops and cafes were operating normally.
Communications Minister Khalid Naciri, who is also the government spokesman, told Reuters: “Today there was a reaction by the authorities who were systematically provoked.”
“They (the protesters) were warned that this protest was illegal but their behaviour was provocative,” he said, without specifying what had provoked the authorities.
He said there had been counter-protests on Sunday in Casablanca, the capital Rabat, and the city of Fez by citizens who wanted to express their anger at the damage to the Moroccan economy caused by the anti-government protests.
Moroccan officials have said previously that Islamists and extreme leftists were seeking to spread unrest under the guise of pro-democracy protests.
Morocco’s ruler King Mohammed announced in March that he will amend the constitution to allow greater democracy and more independence for the judiciary — some of the demands which had been put forward by the protesters.