ISIS Cell Dressed in Police Uniform Kills 31 in Suicide Bomb Attack on Iraq's Tikrit

An Islamic State militant group (ISIS) cell, dressed in police uniforms, launched a coordinated suicide bomb and gun assault overnight on the northern Iraqi city of Tikrit, killing at least 31 people.

Ten or more ISIS fighters, commandeering a police vehicle, entered the city 109 miles north of Baghdad. Two were suicide bombers who detonated their devices, Iraqi police colonel Khalid Mahmoud told Reuters.

The victims of the attack included 14 police officers, while security forces found civilians killed in their shops. At least 42 were wounded. Police killed three attackers in clashes. Five remain in hiding.

Authorities in Tikrit declared a curfew Wednesday in a bid to lockdown the city and locate the remaining attackers.

Iraqi forces and Iranian-backed Shiite paramilitary groups recaptured the city, which was the hometown of deposed Iraqi dictator Saddam Hussein, in March 2015.

Dressing as opposing forces, or using another form of disguise to evade security services, in a conflict is not a new tactic for extremist groups. The Taliban has used the tactic in both Pakistan and Afghanistan to launch assaults, as has the Hamas militant group in cross border raids into Israel from the Gaza Strip. It is a tactic that allows extremists to get closer to their targets, and makes the task of security forces increasingly difficult.

Read more: ISIS militants dressed as doctors attack military hospital in Kabul

ISIS has previously urged the use of disguise. In Fallujah in 2015, a then-contested city now liberated, Iraqi forces found an ISIS pamphlet calling on militants to disguise themselves as security forces.

Last month, ISIS claimed responsibility for an attack on a Kabul military hospital. Its gunmen dressed as doctors to enter the compound, killing 38 people and injuring dozens.

The overnight attack comes a day after ISIS's new spokesman Abu Hasan al-Muhajir released a 36-minute audio message—only his second to date—in which he called on ISIS supporters to "roll up your sleeves" and step up attacks to help the group as it battles against ground forces supported by U.S.-led coalition airpower in both Mosul and Raqqa.

Tikrit, which ISIS overran in June 2014, was the site of one of the worst sectarian massacres in modern Iraqi history. Its fighters led Shiite men to the palace complex of Saddam Hussein, executing 1,700 military personnel from the Camp Speicher base. It then dumped many of their bodies into the River Tigris. Pro-government forces, after liberating the city, discovered almost a dozen mass graves in the surrounding Tikrit area.