While governor in name only, Alp aspired to replace Ghiyath ad-Din Mas’ud as sultan upon his death.
In 1145, Alp conspired to kill Zengi's deputy Naşīr al-Dīn Jaqar and take control of Mosul.
His co-conspirator was likely Farrukh-Shāh ibn Mahmūd, who provided assurances that the army would support Alp.
Naşīr was killed by Alp, Farrukh or their followers (according to different sources), and his head thrown for effect towards Zengi's forces.
Qadi Taj al-Din Yahya ibn Shahrazuri encouraged Alp to take control of the citadel at Mosul, escorting him there, where he and his followers were arrested by Zengi loyalists.