Mimi Theobold, 25, a tourist from England, said she was with friends on a restaurant terrace when the tables began shaking and plates went flying.
Houda Outassaf, a local resident, said she was "still in shock" after feeling the earth shake beneath her feet -- and losing relatives.
"I have at least 10 members of my family who died... I can hardly believe it, as I was with them no more than two days ago," she said.
The interior ministry said authorities have "mobilised all the necessary resources to intervene and help the affected areas".
The regional blood transfusion centre in Marrakesh called on residents to donate blood for those injured.
The army has set up a field hospital in Moulay Brahim and deployed "significant human and logistical resources" to support search and rescue efforts in Al-Haouz, state news agency MAP said.