The United States and Iran are moving rapidly to defend Iraq from rampaging Sunni Islamist insurgents, with Washington urgently considering air strikes on the jihadi militants and Tehran dispatching its foremost powerbroker to help arrange the defence of Baghdad. Senior US officials said that an air campaign was under serious discussion, possibly targeting fighters not just in Iraq but in Syria, where they have seized swaths of territory in the past two years. President Barack Obama said that decisions would be taken in the "days ahead". Iran, meanwhile, moved to defend its own interests in its western neighbour, sending Major General Qassem Suleimani, an éminence grise of the Iranian revolutionary guards, to Baghdad to meet militia leaders and tribal chiefs in control of the Iraqi capital's vulnerable western approaches. The scramble by two staunch adversaries to shore up the embattled Iraqi authorities underscored how seriously they take the situation in a country in danger of fragmentation as a result of this week's sudden advance by fighters from the Islamic State of Iraq and the Levant (Isis). The jihadi grouping, consisting of no more than 7,000 men, has upended regional calculus this week, seizing key Iraqi cities and towns in the north, sending the army fleeing as they sweep south to within 50 miles of the capital. Hundreds of thousands of Iraqis are on the move, seeking safe haven. The UN has warned that the Isis fighters have committed summary executions and rape on their irresistible advance. The next big town in their way is Samarra, known for its Shia shrines. Units of Shia militia were escorted north from Baghdad to defend its holy sites. Fighting was reported in and around the city on Friday. Witnesses said the shrines remained undamaged and that the insurgents had not been threatening residents. "Some of them have long hair and they are carrying black flags," said one man. "They are Arabs from other countries."