Iraqi security forces lost 2,300 Humvee armoured vehicles when the Islamic State of Iraq and the Levant (ISIL) group overran the northern city of Mosul, according to the country's prime minister.

Clashes began in Mosul, Iraq's second city, late on June 9, 2014, and Iraqi forces lost it the following day to ISIL, which spearheaded an offensive that overran much of the country's Sunni Arab heartland.

A day after Haider al-Abbadi's interview was aired on Iraqiya TV, at least 42 Iraqi security forces were reportedly killed in a suicide bombing on an army base north of Fallujah.

Monday's attack was carried out with a explosives-laden armoured Humvee vehicle, which exploded near a weapons depot at the base, military sources told Al Jazeera.

"In the collapse of Mosul, we lost a lot of weapons," Abbadi said in Sunday's interview.

"We lost 2,300 Humvees in Mosul alone."

While the exact price of the vehicles varies depending on how they are armoured and equipped, it is clearly a hugely expensive loss that has boosted ISIL's capabilities.

Last year, the US Department of State approved a possible sale to Iraq of 1,000 Humvees with increased armour, machineguns, grenade launchers, other gear and support that was estimated to cost $579m.

ISIL gained ample arms, ammunition and other equipment when multiple Iraqi divisions fell apart in the country's north, abandoning gear and shedding uniforms in their haste to flee.

ISIL has used captured Humvees in subsequent fighting, rigging some with explosives for suicide bombings.

Iraqi security forces backed by Shia units have regained significant ground from ISIL in Diyala and Salahuddin provinces north of Baghdad.

But that momentum was slowed in mid-May when ISIL overran Ramadi, the capital of Anbar province, west of Baghdad, where Iraqi forces had held out against them for more than a year.