The Arabic TV network Al Jazeera has acquired video evidence of army forces under the control of Syrian President Bashar Assad dropping a barrel bomb out of a military helicopter seemingly onto innocent civilians.

A Syrian soldier pushing a barrel bomb out of a helicopter. Al Jazeera Assad for months has denied using barrel bombs – large oil drums, fuel tanks, or gas cylinders packed with fuel, explosives, and metal fragments for increased lethal effect — despite mounting evidence to the contrary.

This latest bit of damning evidence was filmed from a mobile phone aboard a military helicopter. It shows a soldier using his cigarette to light a barrel bomb before pushing it out of the helicopter.

The phone with the video on it was discovered in the wreckage of a crashed Syrian helicopter and handed over to Al Jazeera, which broadcast it Tuesday night, according to Gov.uk.

"This video footage exposes Assad’s lies on barrel bombs," British foreign secretary Philip Hammond told Gov.uk in response to the video.

"It shows the casual and indiscriminate way in which Syrian regime forces are dropping these horrific weapons out of helicopters onto civilians below. For months we have seen reports of barrel bombs hitting hospitals and schools, killing thousands.

"The UN has called for an end to these attacks, but Assad continues to ignore international outrage," Hammond added. "We will bring those involved in these criminal acts to justice and will continue to help those caught in attacks by continuing our support of rescue teams working on the ground."

Here is what a barrel bomb looks like:

The Syrian government is simultaneously fighting the Al Qaeda affiliate Jabhat al-Nusra, the Islamic State, secular rebel groups, and Kurdish forces in a civil war that has killed upward of 200,000 people since it began four years ago.

Earlier this month Amnesty International released a scathing report accusing Assad of committing crimes against humanity by using barrel bombs on civilians in the city of Aleppo, once the largest city in Syria.

"Civilians in Aleppo are experiencing unthinkable atrocities at the hands of the regime of president Bashar al-Assad," Amnesty International said in its report.

The nonprofit estimates that about 3,100 civilians in Aleppo have died at the hands of Assad since the beginning of 2014.

Watch the full Al Jazeera report here: