By Raheem Salman
BAGHDAD, April 17 (Reuters) - Suspected Sunni Muslim militants killed at least 30 people around Iraq on Thursday including 12 soldiers in an assault on a remote army base in the north, deepening insecurity with a national election just two weeks away.
Sectarian bloodshed has increased since the Shi'ite Muslim-led Baghdad government began an offensive against insurgents, some of them affiliated with al Qaeda, dug in around Falluja and Ramadi in the western province of Anbar.
Early on Thursday morning, gunmen disguised in Iraqi military uniforms drove armoured vehicles, including Iraqi army Humvees, up to a small military base outside Mosul and opened fire, killing 12 soldiers and wounding about a dozen, army and police officers said on condition of anonymity.
An army officer said the armoured cars as well as rocket-propelled grenades, machine guns and some other light weapons used by the militants had been seized during ambushes of Iraqi forces during fighting in Anbar.
The region around Mosul has been a stronghold of the al Qaeda-inspired Islamic State of Iraq and the Levant group. As in Falluja and Ramadi, Iraqi forces face daily skirmishes around Mosul with ISIL and other armed Sunni groups.
Suspected Sunni militants killed another 18 people in bomb and shooting attacks in other parts of Iraq on Thursday.
Meanwhile, a rusting pipeline that runs from the Kirkuk oilfields to the Baiji refinery in Salahuddin province leaked a large amount of oil into the Tigris River, according to a Northern Oil Company official who asked not be named.
The spill stirred panic after someone set the oil ablaze, sending huge clouds of smoke into the provincial capital Tikrit, according to city residents. Ambulances evacuated residents with difficulty breathing.
Much of northern Iraq's pipeline infrastructure is ageing and in need of renovation, and vulnerable to militant attacks. (Reporting By Raheem Salman, Writing by Ned Parker)