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Khalid Mohammed, Associated Press
Iraqi security forces attack Islamic State extremists in the streets of Tikrit, 80 miles (130 kilometers) north of Baghdad, Iraq, Monday, March 30, 2015.

The Iraqi offensive aimed at driving the Islamic State group out of the northern city of Tikrit has been slowed by booby traps, snipers and suicide bombers, but received a powerful boost last week when a U.S.-led coalition began launching airstrikes in support of the operation.

Until now Iraq's beleaguered military -- which crumbled in the face of the IS group's lightning advance last summer -- has relied on Iranian-backed Shiite militias. Several militias announced they would sit out the Tikrit battle once the U.S. strikes began, but fighters wearing mismatched uniforms and waving the groups' flags can still be seen on the front lines.

There on the city's dusty outskirts, Iraqi security forces advance slowly, keeping an eye out for roadside bombs and listening for the telltale crackle of sniper fire. They hole up in abandoned houses shredded by bullet holes, taking shelter from mortar and rocket attacks, sometimes for several hours.

At least four suicide bombers tried to ambush one of their positions in southern Tikrit on Monday, but the attack was repelled.

The battle for Tikrit, Saddam Hussein's hometown, is seen as a key step toward eventually recapturing Mosul, the country's second largest city, which lies further north.

The following is a selection of photos taken in Tikrit by AP photographer Khalid Mohammed, who is embedded with Iraqi forces.

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