Morocco has asked Spain to accredit Souilem Ould Ahmed, a deserter from the Polisario Front, which seeks an independent state in Western Sahara that Rabat claims as its territory.
But Spanish media said the appointment has not been met with enthusiasm in Madrid, with the Madrid government concerned that Ahmed will focus heavily on the Western Sahara conflict at the expense of other issues.
"He arrived today (Saturday)," said the foreign ministry source, confirming reports in Spanish media.
It was not immediately clear when Ahmed may present his credentials to King Juan Carlos.
Moroccan Foreign Minister Taieb Fassi Fihri had said during a visit to Madrid in November that Ahmed would take up his position by the year-end.
Western Sahara, a former Spanish colony annexed by Morocco in 1975, is at the centre of conflict between the Algerian-backed Polisario Front and Rabat, which is willing to accord broad autonomy, but not independence.
During the time that the ambassador post has been empty, tensions between Madrid and Rabat have simmered over the arrest of Spanish nationals for staging a pro-independence protest in mineral-rich territory.
Tensions between the two nations have also mounted over the Spanish enclaves of Melilla and Ceuta on the North African coast. Rabat considers the two enclaves, ruled by Spain for some five centuries, as "occupied cities".
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