The February 20 reform movement also rallied in other Moroccan cities. In the capital Rabat, several hundred marched in support of the reforms.
On Friday, the king proposed slightly loosening his current absolute power.
But he said he would keep total control of Morocco’s security and foreign policy, as well as matters of religion.
King Mohammed VI’s proposals will be put to a referendum on 1 July, but critics say this leaves little time for a real debate.
They want constitutional changes drawn up by a democratically elected committee instead.
Activists say Morocco’s 400-year-old dynasty has a long history of enacting superficial reforms.
Like many countries across the Middle East and North Africa, Morocco has seen a growing call for major reforms to its political system in the past year.
The country has also been facing severe economic challenges with high unemployment and rising levels of poverty.