An Iraqi security official says the crackdown is expected to end Saturday in the northern city, which is considered the last stronghold for al-Qaida in Iraq and other Sunni insurgents.
The official spoke on condition of anonymity Friday because he was not authorized to speak to journalists.
The official says the suspects detained include alleged senior insurgent commanders and financiers. The official says U.S. forces were involved, but mostly in a support role.
It is the latest attempt to break insurgents' grip in the Mosul area. In February, U.S. and Iraqi forces joined in a wide-ranging offensive.