[citation needed] The Tekna tribes speak Hassaniya Arabic and the Berber Shilha dialect in varying degrees.[6] The Tekna are divided into several Berber-speaking and Arabic-speaking tribes, which are organized into two tribal confederations or leff:[7] During the 17th century, Morocco under Sultan Ismail Ibn Sharif seized control over the territory from the Tafna River south to Senegal and Timbuktu.[9] On May 30, 1767, Mohammed ben Abdallah, Sultan of Morocco, signed a peace and commerce treaty with King Charles III of Spain, recognizing that Morocco did not control the Tekna tribes.[10] However, at the time of the Spanish colonization and at the beginning of the 20th century, the Tekna tribes recognized the Sultan of Morocco as their spiritual ruler, but not its political one.[11][verify][verification needed][12][verify][verification needed] (in French) Attilo Gaudio, "Les populations du Sahara occidental: histoire, vie et culture", ed.