Russian claims that a suspected chemical weapons attack in Syria was actually the result of an airstrike that hit a rebel chemical weapons depot drew derision Wednesday at an emergency meeting of the U.N. Security Council.

"There is only one air force that has used such weapons in Syria," British envoy Matthew Rycroft said. "This doesn't look like the work of terrorists. This doesn't look like the work of militants. This carries all the hallmarks of the (President Bashar) Assad regime."

The attack killed more than 70 people, left hundreds more suffering from effects of the gas and drew global outrage. Kremlin spokesman Dmitry Peskov said Russia will press its claim at the emergency meeting.

Maj. Gen. Igor Konashenkov told Russia’s TASS news agency the strike hit a depot containing mines loaded with chemical weapons on the outskirts of the rebel-held town of Khan Sheikhoun, where the deaths occurred.

“The territory of this storage facility housed workshops to produce projectiles stuffed with toxic agents,” Konashenkov said. He said militants sent the chemical weapons from the site to Iraq.

Hasan Haj Ali, commander of the Free Idlib Army rebel group, told Reuters that witnesses on the ground could clearly see the gas bombs.

“We have every indication that this was a sustained attack using aircraft over a number of hours,” Rycroft told the council. “We see all the signs of an attack using a nerve agent.”

Syria denies using poisonous gases and said the army does not possess chemical weapons, state media reported. It said rebels and their supporters "fabricated fake accusations against the armed forces in the Syrian Arab Republic," the SANA news agency reported.

U.N. High Representative for Disarmament Affairs Kim Won-soo opened the Security Council meeting by saying that if the attack is proven to be chemical, it would be the most severe in Syria since hundreds of people were killed in rebel-held suburbs of Damascus in 2013. A proposed Security Council resolution would condemn the use of chemical weapons and press Syria to provide immediate access for investigators to air bases where attacks involving chemical weapons may have been launched.

The Syrian Observatory for Human Rights, a U.K.-based monitoring group, said 72 people died Tuesday, including 20 children. Syrian opposition health minister Firas Jundi put the death toll at more than 100 civilians and said 500 others, mostly children, were sickened or injured by the gas.

The deaths occurred after either chlorine or the nerve agent sarin shrouded parts of Khan Sheikhoun in Idlib province. Human rights reports said the gas appeared to be a virulent deadly strain and covered a wider area than past attacks, with many victims collapsing outdoors.

A Doctors Without Borders medical team providing support to the emergency department of Bab Al Hawa hospital in Idlib has confirmed that patients’ symptoms are consistent with exposure to a neurotoxic agent such as sarin gas, the group said Wednesday.

Pope Francis said Wednesday that he “strongly deplored the unacceptable massacre" “and was "watching with horror the latest events in Syria.”

Nikki Haley, U.S. ambassador to the United Nations, said Tuesday that "more than 60 people, including young children - vomited and gasped for air before they were choked to death - likely at the hands of the Syrian regime."

White House spokesman Sean Spicer said the assault, which burned hundreds of others, "cannot be ignored by the civilized world." He steered blame at the Obama administration in part for "weakness and irresolution" toward Syria. The Trump administration is assessing what action it would take.