In an attempt to drive out anti-government fighters, the Iraqi army has reportedly been dropping barrel bombs on the city of Fallujah, killing civilians, hospital sources and witnesses told Al Jazeera.

The use of barrel bombs in civilian areas is banned under international conventions, given their indiscriminate nature.

Mohammed al-Jumaili, a local journalist, told Al Jazeera that the army has repeatedly dropped barrel bombs "targeting mosques, houses and markets" in Fallujah.

Barrel bombs are simple but destructive — they're oil barrels stuffed with explosives that get dropped from helicopters.

Local hospital sources said the situation was getting worse for many people who had been trapped in the city since the army cut off a key bridge.

Fallujah, just west of Baghdad, is where American soldiers and Iraqis engaged in some of the fiercest fighting of the Iraq war.

With Shia Iraqis in power in Baghdad, the country’s Sunni minority says it feels left out of the country’s decision-making process.

To make matters worse, the civil war in Syria has led to a glut of battle-scarred young men, who slip across the porous border between Iraq and Syria. The Al-Qaeda-linked Islamic State of Iraq and the Levant (ISIL) has been responsible for attacks across western Iraq and eastern Syria.

The Iraqi government has denied the use of barrel bombs and asserted that it was fighting in a "humane way.”

Al Jazeera, however, has obtained photographs showing strong evidence of barrel bomb use.

The Syrian government has made extensive use of barrel bombs, using them to terrify civilians in rebel-held areas, dropping them on hospitals and apartment buildings.