The US has launched airstrikes against targets in Tikrit to support Iraqi ground forces trying to push ISIS militants out of the city, a senior official said. Iraq requested the strikes, which began Wednesday and are 'ongoing,' according to the unnamed US official. An Associated Press correspondent in Tikrit reported hearing warplanes overhead late Wednesday, followed by multiple explosions. Scroll down for video . Stalled ground offensive: Smoke rose over Tikrit, where Iraqi security forces and Shiite militias have battled ISIS militants . Iraq began the Tikrit ground offensive in early March without requesting US air support, even as it welcomed help from Iran. In an address to the nation Wednesday evening, Prime Minister Haider al-Abadi predicted success in Tikrit but did not say the US was providing airstrikes. 'We have started the final phase of the operation in Tikrit,' he said. "You will liberate your ground, not anyone but you," he said, in a speech to the Iraqi people. Al-Abadi praised all the groups involved in the battle against the Islamic State group, including the so-called Popular Mobilization Forces, which the US calls Iranian-backed militias, the Sunni tribes and coalition forces. He fell short of confirming that the coalition is playing a direct role in Tikrit. US airstrikes in Tikrit raise highly sensitive questions about participating in an Iraqi campaign that has been spearheaded by Iraqi Shiite militias trained and equipped by Iran, an avowed US adversary. Difficulties: Militias like the Imam Ali Brigades, one of whose members is shown, have encircled ISIS forces but have been unable to dislodge them from the city . Iran has provided artillery and other weaponry for the Tikrit battle, and senior Iranian advisers have helped Iraq coordinate the offensive. Iraq pointedly did not request US air support when it launched the offensive in early March and recently, the offensive has lost momentum. Col Steve Warren, a Pentagon spokesman, said Wednesday the Iraqi forces have encircled Tikrit but not yet made significant inroads into the heavily defended city limits. 'They are stalled,' he said. The US has hundreds of military advisers in Iraq helping its security forces plan operations against the Islamic State, which occupies large chunks of northern and western Iraq. But the US has said it is not coordinating any military actions with the Iranians. Warren said that at Baghdad's request the US began aerial surveillance over Tikrit in recent days and is sharing the collected intelligence with the Iraqi government. The US-led air campaign, launched in August and joined by several European allies, has allowed Iraqi forces to halt the ISIS group's advance and claw back some of the territory militants seized last summer. Uneasy: Militiamen guarding the front line in the battle between Iraqi forces and ISIS militants, a battle which has 'stalled' recently . But the growing Iranian presence on the ground has complicated the mission, with Washington refusing to work directly with a country it views as a regional menace, yet is currently embroiled with Iran in sensitive negotiations over a nuclear deal. The prominent role of the Shiite militias in the fight to retake Tikrit and other parts of Iraq's Sunni heartland has meanwhile raised concerns that the offensive could deepen the country's sectarian divide and drive Sunnis into the arms of the Islamic State group. Hadi al-Amiri, leader of the Badr Organization and a commander of Iraq's Shiite militias, told reporters in Samarra: . 'If we need them (the US-led coalition ) we will tell them we need them. But we don't need the coalition. We have surveillance planes over our heads already. The participation of U.S. planes hinders out operations... If we need it, we'll tell our government what we need.' He claimed that the militias, the overwhelming majority of which is made up of Shiite fighters, have their own surveillance drones. 'We buy them anywhere,' he said. 'We have our own ... controlled by Iraqis.' A series of US airstrikes north of Tikrit, in the vicinity of Beiji, in recent weeks has had the indirect benefit of tying down ISIS forces that might otherwise be operating in defense of Tikrit. On Wednesday, for example, the US military said it had conducted five airstrikes Tuesday near Beiji, home of a major oil refinery that ISIS has sought to capture. That bombing targeted ISIS combat units and destroyed what the US called an ISIS 'fighting position,' as well as an ISIS armored vehicle. Warren said the Iraqis are discovering how difficult it can be to carry out ground operations in an urban area. 'We heard quite a bit from the Iraqis and some even from the Iranians — some fairly high-confidence statements about how rapidly the operations for Tikrit would go," Warren said. "We've seen otherwise.' 'I think it's important that the Iraqis understand that what would be most helpful to them is a reliable partner in this fight against ISIL,' Warren said. 'Reliable, professional, advanced military capabilities are something that reside very clearly and very squarely with the coalition.'
Iraq requested the airstrikes to support an offensive begun in early March . At the outset of the offensive, the Iraqi forces declined US-led coalition support though it looked to Iran for weapons and artillery . A Pentagon spokesman said the offensive has 'stalled'