Shi’ite Iran says it will consider working with longtime foe the United States if it takes the lead in pushing back Sunni Arab militants, who have seized a swathe of northern Iraq.

Saturday’s offer came as Iraqi commanders said the army had recaptured two towns north of Baghdad as they prepared a fightback, bolstered by thousands of Shi’ite volunteers who have signed up in response to a call to arms by top cleric Grand Ayatollah Ali al-Sistani.

Prime Minister Nuri al-Maliki visited the besieged shrine city of Samarra on Friday to rally troops and pray at the Al-Askari mausoleum, a revered Shi’ite shrine whose 2006 bombing by al-Qaeda sparked sectarian conflict that killed tens of thousands.

President Barack Obama said he was “looking at all the options” to halt the offensive that has brought jihadist-led militants within 80km of Baghdad city limits but ruled out any return of US combat troops.

“We will not be sending US troops back into combat in Iraq but I have asked my national security team to prepare a range of other options that could help support Iraqi security forces,” he said.

Obama has been under mounting fire from his Republican opponents over the swift collapse of the Iraqi security forces, which Washington spent billions of dollars training and equipping before pulling out its own troops in 2011.

Iranian President Hassan Rouhani, who since taking office last August has overseen a rapprochement with a superpower Tehran long derided as the “Great Satan,” said his government was prepared to consider offering help.

“If we see that the United States takes action against terrorist groups in Iraq, then one can think about it,” Rouhani told a press conference.

The Iraqi cabinet has granted the Shi’ite premier “unlimited powers” to reverse the lightning offensive, which has seen the militants sweep down towards Baghdad after overrunning second city Mosul on Tuesday.

Troops and tribal militia found the burned bodies of 12 policemen as they recaptured the town of Ishaqi in Salaheddin province from Sunni Arab insurgents, a police colonel and a doctor said.

It was one of the closest points to the capital the militants had reached in the offensive that saw them overrun a large chunk of northern and north-central Iraq this week.

Troops also retook the nearby Muatassam area of Salaheddin, the colonel said.

On Friday night, police and residents expelled militants from another town in the province, Dhuluiyah, where they had set up checkpoints, witnesses said.

“Residents are now firing into the air” in celebration, witness Abu Abdullah said.

Security forces have also held fast in the Muqdadiyah area of Diyala province, preventing militants from taking the town in heavy fighting, a police colonel said.

In Samarra, reinforcements were awaiting orders to launch a counter-offensive against areas north of the city, including Dur and Tikrit, seized by the militants earlier this week, an army colonel said.