Tikrit University
A general view shows Tikrit University, where Iraqi special forces clashed with fighters from the Islamic State in Iraq and the Levant (ISIL) last month on July 18, 2014. Reuters

(Reuters) - Iraqi forces launched an operation on Tuesday to drive Islamic State militants out of Tikrit, hometown of executed former dictator Saddam Hussein, officers in the operations room told Reuters.

They were advancing rapidly from the south but were slowed by landmines, roadside bombs and snipers in the west, said an army major and a police captain.

Iraqi and Kurdish forces have been encouraged by the first U.S. air strikes in the country - launched against the hardline Sunni insurgents - since American troops withdrew in 2011.