At least five people are believed to have died in a chemical attack carried out by forces loyal to Syrian President Bashar Assad, opposition activists alleged Wednesday. The attacks were reportedly carried out Tuesday in the rebel-held Damascus suburb of Muadhamiya, where in 2013 the nerve agent sarin was used in an attack that killed hundreds of people.

“The Assad regime again used chemical weapons against civilians in Moadamiyet [Muadhamiya] earlier today, with regime warplanes dropping barrel bombs containing a so-far unidentified toxic gas on the south of the town,” a local activist group, whose name was not revealed, told Agence France-Presse (AFP). “Five people have died so far as a result with others suffering severe breathing problems.”

The Syrian National Coalition, the main opposition group in the country, also confirmed that government forces had dropped barrel bombs containing “unidentified chemical weapons,” suggesting that Assad might still be in possession of sarin — a direct contravention of United Nations resolutions condemning the 2013 attack as a war crime, and a breach of the Syrian government’s vow to destroy its chemical weapons stockpile.

"While the Syrian Coalition strongly condemns this crime, it denounces the international community’s silence over this heinous act," the coalition said, in a statement released Wednesday. "This continued silence is seen by Assad as a green light to commit more crimes against the Syrian people."

Photos and videos purportedly showing men with blood around their mouths and noses being rushed to a hospital also emerged after the alleged attacks. However, while the U.K.-based Syrian Observatory for Human Rights said that an attack had taken place, it could not confirm the use of a toxic gas.

Meanwhile, a government source told AFP that the allegations were “baseless.”

“This is a cheap ruse and a broken record that they are using in an attempt to justify their defeats,” the source, whose name was not revealed, said.

Over the past year, the Organization for the Prohibition of Chemical Weapons has documented the use of toxic chemicals, such as chlorine and ammonia, in a series of deadly attacks on rebel-held Syrian villages. However, the Syrian government has consistently denied using chemical weapons and has blamed “terror groups,” including the Islamic State group, for the use of such weapons.