In a brief video clip provided to The Independent, white smoke lit by fire billows over a dark line of trees and buildings, and explosions can be heard.
According to the commentary of the unseen cameraman, it shows the impact of "phosphorous bombs from Russian planes" on the village of Umm al-Karamil in the south Aleppo countryside.
A series of still photographs appear to show the characteristic white streaks of incendiary munitions descending through the air, and large numbers of small craters apparently scorched in the Syrian countryside by submunitions. The footage could not been independently verified.
A Russian embassy spokesperson said: "Russia has never used any forbidden weapons or ammunition in Syria.
"These materials, that cannot be verified, are published at the discretion - and responsibility - of those who do it."
The embassy's claims appear contradictory to previous media reports. Last year, the Washington Post reported Russia had edited out footage of Russian jets armed with incendiary munitions from a state-funded TV channel.
Though the activists described the munitions as "white phosphorous" to The Independent, Human Rights Watch research suggests the Syrian-Russian coalition tends to use thermite-based incendiary weapons, which start fires when they land and cause excruciating burns if contact is made with the skin.
The latest pictures and videos purportedly showing incendiary munitions were captured by Ali Hammadeh, a former lawyer who is now a media activist working alongside Syria's White Helmets civil defence organisation. They were sent via another Syrian lawyer, who is now living in Dusseldorf in Germany as a refugee from the Assad regime.
The village is in a rural southern region of Aleppo Governate, 20 miles from the outskirts of Aleppo city and 12 miles from the rebels' last remaining stronghold, Idlib. In 2004, it had a population of 1,147.
According to a live map of the Syrian conflict, Umm al-Karamil is currently held by what remains of the Free Syrian Army. The front with the Russian-backed Assad regime is only five kilometres away.
Islamist groups such as Jabhat Fateh al-Sham, formerly the al-Nusra Front, have made significant territorial gains in Southern Aleppo and nearby Idlib in recent months, but their sphere of influence is not thought to extend this close to regime-controlled areas.
The Independent has ascertained that incendiary munitions were being dropped and that the date and location of the footage is accurate, though it is plausible that the planes could also be part of Assad's Syrian airforce.
Unlike Syria, Russia is a signatory of a United Nations protocol which bans the use of all air-dropped incendiary munitions in areas where civilians are concentrated.
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