Islamic State attacks checkpoints in Iraq's Samarra
Islamic State militants have attacked Iraqi security forces in the central city of Samarra, killing two people and injuring 28 others, officials say.
They reportedly carried out five suicide bomb attacks on checkpoints along a motorway west of Samarra.
The bombings were followed by mortar attacks on the city itself.
IS surrounded Samarra, a predominantly Sunni city that is home to one of Shia Islam's holiest sites, after launching an offensive in northern Iraq in June.
Soldiers and allied Shia militiamen have managed to stop the jihadists overrunning the city, and have recently retaken towns and villages to the south with the help of US-led coalition air strikes.
The latest assault on Samarra by IS militants, who regard Shia as heretics who should be killed, began before sunrise on Thursday.
Two policemen and a civilian were killed when pick-up trucks carrying water tanks filled with explosives were driven towards the checkpoints and blown up.
It is not clear how many of them reached their targets, but they were followed by mortar attacks on the city and an assault by gunmen.
After several hours of battling the security forces, the gunmen are reported to have retreated under fire from Iraqi warplanes.
The destruction of the al-Askari shrine in Samarra in 2006 by al-Qaeda in Iraq, a precursor to IS, is widely considered a key moment in triggering years of sectarian violence in which tens of thousands died.
The reconstruction of its golden dome and minarets is almost complete and many believe IS wants to destroy it again. Mortar shells have landed within 15m (50ft) from the shrine's entrance.
IS considers shrines idolatrous and has blown up or desecrated several in parts of Iraq and Syria it controls. The UN Educational, Scientific and Cultural Organisation (Unesco) has said the "intentional and systematic destruction of cultural heritage" is unprecedented.