BAGHDAD - Iraqi soldiers and allied Shiite militiamen swept into the Islamic State-held city of Tikrit on Wednesday, launching a two-front offensive to squeeze extremists out of Saddam Hussein's hometown in a major test of the troops' resolve.

Explosions and heavy gunfire echoed through Tikrit, a key way station for Iraqi forces trying to expel the militants who hold roughly a third of the country and neighboring Syria. The offensive also will serve as a major crucible for Iraqi forces, which collapsed under the extremists' initial offensive last year and now face street-by-street fighting in one of the Islamic State's biggest strongholds.

Allied Iraqi forces first entered the city through its northern Qadisiyya neighborhood, according to video obtained by the Associated Press. Overhead, an attack helicopter fired missiles as soldiers and militiamen laid down heavy machine-gun fire in the neighborhood's dusty streets as downtown Tikrit loomed in the distance, black smoke rising overhead.

Supply line

Officials quickly established a supply line through the neighborhood to reinforce troops, Salahuddin Police Brig. Kheyon Rasheed told the state-run Iraqiyya television. Authorities offered no immediate casualty figures, though Iran's state-run Press TV satellite channel reported that a mortar attack wounded one of its cameramen there.

A local official in Iraq's Salahuddin province confirmed that Iraqi troops entered Qadisiyya and raised the Iraqi flag over Tikrit's general hospital. He spoke on condition of anonymity as he was not authorized to brief journalists.

'A getaway'

Later Wednesday, allied forces also swept into Tikrit from the south in a pincer movement to squeeze out militants, though some suggested many already fled in the face of the advance, code-named "At your service, prophet of Allah."

"The terrorists are seizing the cars of civilians trying to leave the city and they are trying to make a getaway," Rasheed said.

Tikrit, the capital of Salahuddin province, sits on the Tigris River about 80 miles north of Baghdad. Several of Saddam's palaces remain there, as do remnants of his now-outlawed Baathist party. Many believe party members assisted the Islamic State group in its offensive last summer.

After the 2003 U.S.-led invasion, Baathists in Tikrit launched attacks on American forces. The same could happen to incoming Iraqi forces, who already faced sniper fire and heavily mined roads.