The pre-Turkic population that lived on the territory of modern Azerbaijan spoke several Indo-European and Caucasian languages, among them Armenian and an Iranian language, Old Azeri, which was gradually replaced by a Turkic language, the early precursor of the Azerbaijani language of today. Some linguists have also stated that the Tati dialects of Iranian Azerbaijan and the Republic of Azerbaijan, like those spoken by the Tats, are descended from Old Azeri. Locally, the possessions of the subsequent Seljuk Empire were ruled by Eldiguzids, technically vassals of the Seljuk sultans, but sometimes "de facto" rulers themselves. Under the Seljuks, local poets such as Nizami Ganjavi and Khaqani gave rise to a blossoming of Persian literature on the territory of present-day Azerbaijan.