A few hundred people, mainly youths, attended a quickly improvised pro-democracy rally in front of the Moroccan parliament, calling for the rule of law and radical political reform.
The demonstration, called on social networking site Facebook, was backed by human rights activists who gathered on Sunday in central Rabat before heading for the parliament building.
They gathered for a few just minutes, many making the V for victory sign, before dispersing.
Another demonstration in Morocco's biggest city Casablanca drew several hundred people, an AFP correspondent witnessed.
They carried placards reading "Dignity" and "Social Justice" and denouncing the concentration of money and power. Last weekend nearly 1,000 people rallied in Casablanca despite a heavy police.
Among those attending the rally were many members of the Islamist Justice and Charity movement, which while not officially recognised in Morocco is tolerated.
Another rally in the northern port of Tangiers drew about 100 people.
Security sources moved in to break up a group of youths who tried to disrupt the rally, said local officials.
Young activists campaigning for greater democracy in Morocco have used Facebook to call for new demonstrations on March 20. They want to limit the powers of the monarchy.
A previous call brought out thousands of people across the country on February 20, the first in the country since the start of the uprisings across the Arab world this year.
King Mohammed VI's advisor, Mohammed Moatassim, told union leaders last week that the monarch wanted reforms, without specifying what they would be or when they would be introduced.