The US and its allies have conducted 22 air strikes against Islamic State militants in Syria and Iraq during the past 24 hours.

The strikes come as 17 Iraqi troops were killed by IS suicide bombers in the city of Fallujah.

Four suicide bombers drove vehicles with explosives into an army barricade just outside the city, sparking fighting between the two sides.

At least 15 other troops were injured, according to officials.

The US responded to Islamic State manouevres with three airstrikes strikes on targets near Hasaka in northeast Syria.

Another strike near Aleppo struck an Islamic State tactical unit, and a further strike hit a tactical unit and destroyed three fighting positions near Kobani, near the Turkish border, according to the Coalition Joint Task Force.

As well as hitting militants in Fallujah, the US war planes also targeted Iraqi IS positions in Baiji, Mosul, Ramadi, Sinjar, and other areas.

Fallujah is about 42 miles west of Baghdad and its fall in January last year sparked the militant group's stampede when it captured swathes of the country and moved deeper into Anbar province, home to many of the country's Sunni minority.

The province's capital Ramadi fell in May after more than a year of fighting but Iraqi media reported that Iraqi troops, backed by tribal fighters and others, are close to re-taking the city from the militants, closing in on it from three directions.

Local media reported that volunteer fighters have already managed to retake the Khamsa Kilo district of Ramadi, part of a wider battle to retake Anbar province before heading to Mosul, Iraq's second-largest city, also held by IS.

Central Command spokesman Colonel Pat Ryder confirmed that Iraqi security forces are "encircling" Ramadi, in order to "tighten the noose around ISIL's neck in this city before commencing...the seize aspect of the operation".

It came as Iraq's Prime Minister Haider al-Abadi slashed his cabinet from 33 members to just 22, in response to mass protests against corruption and poor governance.