Russia has said that it has warned the US of "grave repercussions" if it attacks Syria over claims of a chemical weapons attack.

"There was no chemical weapons attack," said Russian UN Ambassador Vassily Nebenzia during a UN Security Council meeting held on Monday.

"Through the relevant channels we already conveyed to the US that armed force under mendacious pretext against Syria – where, at the request of the legitimate government of a country, Russian troops have been deployed - could lead to grave repercussions," he added.

He added that investigators with the global chemical weapons watchdog should travel to Syria as early as Tuesday to investigate accusations concerning the attack.

"Our military, radiological, biological, chemical unit was on site with the alleged chemical accident and it confirmed that there was no chemical substances found on the ground. There were no dead bodies found. There were no poisoned people in the hospitals. The doctors in Douma denied that there were people who came to the hospital claiming that they were under the chemical attack. The Syrian Red (Crescent) that was said to be treating people which were poisoned denied that it was ever doing that today. So what we're saying -- we are requesting the OPCW (Organization for the Prohibition of Chemical Weapons), which said in the person of its director general that they were ready to go to Douma, to do it immediately and to see themselves what happened on the ground," he added.

An alleged chemical attack on Saturday in the militant-held town of Douma in Eastern Ghouta reportedly left dozens dead.

Damascus, in a statement released late on Saturday, strongly rejected the allegation of using chemical munitions and said that the so-called Jaish al-Islam Takfiri terrorist group, which has dominant presence in Douma, was repeating the accusations “in order to accuse the Syrian Arab army, in a blatant attempt to hinder the Army’s advance.”

US will respond to attack: Haley

During the UNSC meeting, US Ambassador to the United Nations Nikki Haley said that Washington "will respond" to incident regardless of whether the United Nations Security Council takes action or not.

"We have reached the moment when the world must see justice done," she said.

"History will record this as the moment when the Security Council either discharged its duty or demonstrated its utter and complete failure to protect the people of Syria...Either way, the United States will respond," she added.

US Ambassador to the UN Nikki Haley speaks during the United Nations Security Council meeting on threats to international peace and security and the situation in the Middle East April 9, 2018 in New York. (Photo by AFP)

Syria once again denies chemical attack

Also present at the meeting, Syria's ambassador to the United Nations Bashar Ja'afari once again denied that Syria was involved in a alleged chemical weapons attack in Douma.

"The Syrian Arab Republic stresses once again that it does not possess any chemical weapons of any type, including chlorine, and we condemn once again the use of chemical weapons at any time anywhere and under any circumstance," he said.

Syria's Ambassador to the United Nations, Bashar Jaafari addresses the United Nations Security Council meeting on Syria at the U.N. headquarters in New York, US, April 9, 2018. (Photo by Reuters)

"The Russian Center for Reconciliation in Syria announced today that military experts have carried out investigations in Douma, and these investigations suggest that there are no signs of the use of chemical weapons there. And while treating the sick that are being treated in the hospitals of Douma, Russian doctors have proven that these patients have not been subjected to any chemical substance. So what we are witnessing here is really a Hollywood scene. Thank you, Mr President," he added.

Ja'afari further condemned an Israeli attack on a Syrian military airbase in Homs province.

"The government of the Syrian Arab Republic condemns in the strongest terms the ruthless Israeli aggression that took place this morning on the airport in Homs governorate, killing and injuring a number of civilians," he said.