Human rights advocates are condemning the use of incendiary weaponry—including phosphorous bombs—in airstrikes conducted by the Syrian regime and the Russian government on the cities of Aleppo and Idlib on August 7.

"It was so bright you could see the buildings as if was daylight. It was absolutely abnormal. Honestly, words cannot describe it."

—Syria Civil Defense volunteer in Idlib, SyriaAnd a new proposal for joint U.S.-Russia airstrikes would make a horrific situation even worse, a local aid worker warns.

"I saw with my own eyes two strikes, both 'phosphorus'—blocks of flame were falling from the sky," said Ala' Abdel Aziz Hmeidan, an Idlib resident, to rights group Human Rights Watch (HRW), describing phosphorous bombs falling on the city. "After that, there was a strike with a missile carrying cluster bombs. It was tragic, buildings were on fire, rocks were on fire."

In a press briefing published Tuesday, HRW notes: "Local activists, human rights organizations, first responders, and media organizations have reported the use of incendiary weapons on at least 40 other occasions, but no photographs and video footage were available, so Human Rights Watch could not conclusively determine if incendiary weapons were involved." In this case, video and photographic evidence captured by locals confirmed the use of incendiary weapons on August 7.

A Syria Civil Defense volunteer who responded to the attack in Idlib described it in great detail to HRW:

The fire was vast, spreading hundreds of meters, difficult to put out. It reacted with water so we had to use other material, like foam and powder, even gravel. The fire took over everything, houses, cars, oil tanks, and even grass. We heard explosions. It was huge, it required immense efforts to extinguish. The tall, crowded buildings did not make things easy. It took us around an hour to control the situation. It was so bright you could see the buildings as if was daylight. It was absolutely abnormal. Honestly, words cannot describe it.

Hmeidan told the rights organization that the areas bombed in Idlib are largely residential and there were no armed groups present at the time of the strike.

"The disgraceful incendiary weapon attacks in Syria show an abject failure to adhere to international law."

—Steve Goose,

Human Rights Watch"Incendiary weapons produce heat and fire through the chemical reaction of a flammable substance, causing excruciatingly painful burns that are difficult to treat," HRW explains. "The weapons also start fires that are hard to extinguish, destroying civilian objects and infrastructure."

"The disgraceful incendiary weapon attacks in Syria show an abject failure to adhere to international law restricting incendiary weapons," added Steve Goose, arms director at HRW. "The resulting civilian harm demonstrates the inadequacy of existing law on incendiary weapons, which should be strengthened urgently. From a humanitarian standpoint, a global ban on incendiary weapons would provide the best solution."

The human rights organization delved into the technical details of such bombs, noting that all the incendiary weapons recorded in Syria so far appear to be ZAB-series (Zazhigatelnaya Aviatsionnaya Bomba) manufactured by the former Soviet Union:

ZAB-series bombs contain a substance believed to be thermite that ignites while falling, leading witnesses to describe the incendiary submunitions as "fireballs." It is not napalm or white phosphorus, which are notorious flammable substances used in other incendiary weapons. The majority of witness accounts collected by Human Right Watch and video evidence indicate that fixed-wing jet aircraft and helicopters have been used to deliver air-dropped incendiary weapons in Syria. There has been at least one incident involving the use of a surface-launched incendiary weapon. The Syrian government has used factory-made incendiary weapons since November 2012, particularly air-dropped bombs manufactured by the Soviet Union such as RBK-250 series bombs and ZAB-100-105 bombs. Syrian government forces have also used air-dropped weapons consisting of improvised canisters or "barrel bombs" filled with a napalm-like flammable substance. Footage broadcasted by Russian state media on June 18 shows RBK-500 ZAB-2.5SM incendiary bombs mounted on a Su-34 fighter-ground attack aircraft at the Russian air base at Hmeymim, southeast of Latakia city, in Syria. Only the Russian air force operates this type of aircraft in Syria.

News of Russia's use of incendiary weapons comes at the same time that joint U.S.-Russia airstrikes against rebel groups are being proposed. An aid worker interviewed by The Intercept said that such a collaboration would be "ludicrous and diabolical."

The Intercept explains that in the past several months, "the United States has repeatedly signaled plans to strike opposition forces in Syria, largely due to fears that al Qaeda-linked groups were making gains in the conflict."

Tauqir Sharif, who works with several British aid organizations in Aleppo, described the current devastation in the city—and warned against the U.S. joining the attacks on rebel groups:

Both Russia and Syrian government are bombing the city right now, we can tell because before the Russian intervention certain weaponry was never seen in Syria: now have seen white phosphorus, cluster bombs, as well as unexploded weaponry with Russian markings. In the only children's hospital left in East Aleppo the conditions are absolutely horrific; it has moved underground to protect it from bombing but there is little oxygen and if a fire were to start no one would be able to escape.

"Exhorting the United States not to join the bombing campaign," The Intercept reports, "Sharif said that officials contemplating such moves had fundamentally misunderstood what the conflict was about."

Sharif told the outlet: "Most people in this city did not even originally want to overthrow the government. They just wanted reforms, but they've been forced to fight because of the regime’s brutal response to their dissent."