Officials said as many as a million people demonstrated
Tens of thousands of Moroccans have thronged the streets of Casablanca to voice their anger over the suicide attacks which killed 43 people.
Dozens of associations and political parties joined the march, led by Prime Minister Driss Jettou and other government officials.
The demonstration began outside the Farah Hotel - one of the targets of the 16 May bombings.
The city centre became a sea of red-and-green Moroccan flags and echoed to the chants of "Down with hate!" and "United against terrorism!"
All 15 suicide bombers are said to have come from the same slum district of Casablanca - Sidi Moumen.
Police are hunting for nine suspected Islamic militants
Moroccan civic groups had originally called the demonstration to protest not only against the bombings, but also against the economic and social conditions prevailing in some parts of the city, which they say helped to foment them.
A large crowd from Morocco's Jewish communities joined the march and demonstrators defended the country's "mosaic of cultures," the French news agency AFP reports.
A Jewish community centre was among the targets of the five co-ordinated explosions.
The deadliest explosion ripped through a Spanish social club called Casa de Espana.
Jewish community leader Serge Berdugo said on Sunday he was "proud" of the massive protest against terrorism.
The Moroccan authorities have said they believe the attacks were the work of Islamic groups working on instructions from al-Qaeda.
They say two of the 14 people identified as playing a part in the attacks are under arrest.
Agents from the US, plus Spain and France - who both lost nationals in the attacks - and Belgium, whose consulate was among the targets, have sent intelligence experts to the country.