"An Historical Atlas of Central Asia" written by Yuri Bregel. This is stated on Page no 31 of this book.

The Seljuk sultan Malik Shah and his vizier Nizam al-Mulk died in 1092. After two years of fighting for the throne between two contenders, the winner, Malik Shah’s son Berk-Yaruq, became the new sultan. His reign, which lasted twelve years (until 1105), was a time of internal feuds and warfare. Arslan-Arghun, who had been appointed governor of Khorezm by Alp-Arslan but under Malik Shah held another post, rebelled and was defeated with some difficulty. Later, Berk-Yaruq had to fight his brother Muhammad Tapar for supreme authority. After the death of Berk-Yaruq, Muhammad became the sultan; he ruled the western part of the empire, while his half-brother Ahmad Sanjar, based first in Balkh and later in Merv, ruled Khorasan and other provinces in the east as a viceroy with the title malik. After the death of Sultan Muhammad in 1118, Sanjar became the supreme sultan of the Seljuks, but the empire was now effectively divided into the eastern sultanate (which included, besides Khorasan, also Mazanderan, Damghan, and Rayy), under Sanjar, and the western sultanate centered in Iraq, under Sanjar’s nephew Mahmud. In 1119, after being defeated by Sanjar, Mahmud acknowledged Sanjar’s supremacy. Sanjar interfered several times in the affairs of the Qarakhanids, primarily of the Western Qaghanate, which remained a Seljuk vassal; but even the Eastern Qarakhanids recognized his overlordship.
In 1130 Sanjar came with an army to Mavarannahr to reinforce the authority there of his Qarakhanid vassal, Arslan Khan Muhammad II. In 1132 he placed on the throne in Samarqand Arslan Khan Mahmud, who was his nephew.
Sanjar also interfered in a succession dispute among the Ghaznavids: answering an appeal by the Ghaznavid Bahram Shah, he conquered Ghazna in 1117, sacked the city, and placed Bahram Shah on the throne; the latter agreed to become Sanjar’s vassal and to pay an annual tribute. In Khorezm, the Khorezmshah #Ala" ad-Din Atsïz, the son and successor of Qutb ad-Din Muhammad, recognized Sanjar’s suzerainty; at the same time he was enlarging his domain, extending his authority over the Turkmens of the Üst-Yurt and Mangïshlaq, and in the delta of the Sïr-Darya, including Jend. In 1138 Atsïz rebelled, provoking a punitive expedition by Sanjar; the army of Atsïz was routed and he fled. Sanjar appointed his own governor for Khorezm, but the following year, as soon as Sanjar returned to Merv, Atsïz returned to Khorezm and banished Sanjar’s governor. He again acknowledged himself as Sanjar’s vassal, but, nevertheless, within a year, in 1139 attacked Bukhara, captured the city, and demolished its citadel and walls; this attack brought no reprisals from Sanjar.