Thousands of Moroccans on Friday defied a government ban and demonstrated in the former mining town of Jerada demanding an "alternative economy" and the release of jailed activists.
The accidental deaths in December of two brothers trapped in a mine shaft, followed by two other deaths under similar circumstances, has sparked a wave of unrest and protests in the impoverished town.
An economic plan proposed by the government succeeded in briefly calming social unrest, but protesters returned to the street in late February to demand concrete solutions.
Tension rose last weekend after authorities arrested four activists.
On Wednesday protesters clashed with police, with authorities saying a "confrontation" began after hooded youths threw stones at law enforcement agents. Activists accused police of assaulting protesters.
The authorities then announced a ban on "illegal protests" and the interior ministry has promised "firm responses to aggressive and irresponsible behavior".
But protesters were back on the streets Friday even as security forces deployed in the town, AFP correspondents said.
At first a small group of demonstrators gathered in the Manar district, where protest leaders live, but they were quickly joined by others, including women and children.
The crowd swelled to several thousand and marched to the police station with protesters waving Moroccan flags and others chanting the national anthem, the correspondents said.
"We are patriotic. But what we want are the most basic rights," one demonstrator said.
"The people here are very poor and have nothing to lose," said another who only gave his first name, Hassan.
He said the protest movement will remain "peaceful" while behind him the crowd chanted slogans demanding "an alternative economy" for the former coal mining town.
Hundreds of illegal miners risk their lives in abandoned mine shafts to extract coal, the sale of which is legal thanks to operating permits issued by Moroccan authorities.
Omar Balafrej, a member of parliament who joined the protest, said he visited the mine shafts in the town.
"It's as if we were in the 19th century," said Balafrej. "There are huge problems in this region and it is a duty to come here and get to know this town".