Militants attacked Iraq's main oil refinery early Wednesday as they pressed an offensive that has seen them capture swathes of territory, a manager and a refinery employee said.
Clashes erupted at around 4:00 am (0100 GMT) at the Baiji refinery in Salaheddin province, north of Baghdad, and some tanks containing refined products caught fire.
A senior manager of the state-owned North Oil Company said militants attacked parts of the refinery complex, leading to heavy clashes.
A refinery employee said there had been casualties among security force personnel and that staff had fled.
Officials told AFP on Tuesday that the refinery had been shut down and many employees evacuated, because major towns seized by the militants, including second city Mosul, were no longer being supplied with refined products.