Spain calls on Morocco to explain disputed enclaves comments
US President Donald Trump earlier this month fulfilled a decades-old goal of Morocco by backing its contested sovereignty over the region.
Rabat in return agreed to normalise ties with Israel under US-brokered deals.
Spain has called for respect of the UN resolutions on the Western Sahara which call for a referendum on self-determination for the region.
In comments on the Saudi network Al-Sharq on Saturday, Moroccan Prime Minister Saad-Eddine El Othmani proposed opening the issue of sovereignty over Ceuta and Melilla.
"Ceuta and Melilla is a question that must be opened... It remains suspended for five or six centuries, but one day it could be opened."
The comments caused unease in Spain, where the foreign ministry summoned Morocco's ambassador to Madrid.
"Spain expects from all its partners the respect of its sovereignty and territorial integrity and called (the ambassador) to explain the statements of the Moroccan prime minister", the ministry said in a statement on Monday.
The tiny enclaves of Melilla and Ceuta, on the northern coast of Morocco, have been under Spanish sovereignty since the 16th and 17th centuries respectively.
They constitute the only Spanish territory on the African continent.
But Morocco considers them to be an integral part of its territory.
Asked in the interview if Rabat believes there is a link between the issue of the Western Sahara and that of Ceuta and Melilla, El Othmani said he believes there is.
But he said the "most important thing is to build coexistence and that the Spanish position on the Western Sahara is moderated."