Battle for Tikrit

A Shi'ite fighter known as Hashid Shaabi, runs as smoke rises from an explosives-laden military vehicle driven by an Islamic State suicide bomber which exploded during an attack on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

Shi'ite fighters known as Hashid Shaabi walk as smoke rises from an explosives-laden military vehicle driven by an Islamic State suicide bomber which exploded during an attack on the southern edge of Tikrit March 12, 2015.

Shi'ite fighters known as Hashid Shaabi run with their weapons after an explosives-laden military vehicle driven by an Islamic State suicide bomber exploded during an attack on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

A Shi'ite fighter known as Hashid Shaabi walks near the flag of the Shi'ite fighters on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

Shi'ite fighters known as Hashid Shaabi run with their weapons as smoke rises after an explosives-laden military vehicle driven by an Islamic State suicide bomber exploded during an attack on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

Shi'ite fighters known as Hashid Shaabi ride in a military vehicle on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

Shi'ite fighters known as Hashid Shaabi gather as smoke rises from an explosives-laden military vehicle driven by an Islamic State suicide bomber, which exploded during an attack on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

A Shi'ite fighter known as Hashid Shaabi keeps watch on the frontline, on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

Shi'ite fighters known as Hashid Shaabi look at smoke from an explosives-laden military vehicle driven by an Islamic State suicide bomber which exploded during an attack on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

Shi'ite fighters, known as Hashid Shaabi, keep watch with their weapons from the frontline on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

Shi'ite fighters known as Hashid Shaabi gather with their weapons as smoke rises from an explosives-laden military vehicle driven by an Islamic State suicide bomber which exploded during an attack on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

Shi'ite fighters known as Hashid Shaabi walk with their weapons on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

A Shi'ite fighter known as Hashid Shaabi runs with his weapon as smoke rises from an explosives-laden military vehicle driven by an Islamic State suicide bomber, which exploded during an attack on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani

Shi'ite fighters known as Hashid Shaabi gather with their weapons as smoke rises from an explosives-laden military vehicle driven by an Islamic State suicide bomber which exploded during an attack on the southern edge of Tikrit March 12, 2015. REUTERS/Thaier Al-Sudani