The Trump administration is accusing Syria of burning thousands of bodies at a prison near Damascus to cover up mass murders.
The State Department released newly declassified commercial satellite photos of what it said is a building at the prison used as the crematorium.
The allegation came as President Donald Trump is weighing options in Syria, where the US attacked a government air base last month in response to an alleged chemical weapons attack on civilians.
The allegations are "a new Hollywood plot" to justify US intervention in Syria, a statement from the Foreign Ministry said. "But then the USA should understand that it bears a hefty responsibility for the future of the peace process in Syria", he said.
The State Department distributed overhead photographs it said documented the gradual construction of the facility outside the main prison complex and its apparent use this year.
However, the gathering in the Swiss city has been overshadowed by U.S. State Department accusations that the Syrian government built a crematorium in one of its most notorious prisons to cover up dozens of daily executions there. He also said he was not suggesting that either Russian Federation or Iran was involved with the facility.
Stuart Jones, acting assistant secretary for Near Eastern Affairs, showed journalists a series of aerial photographs he said indicted the presence of a crematorium at the Sednaya military prison on the outskirts of the capital Damascus, Reuters reports.More news: Rajnath Singh speaks to Parrikar over Goa bridge collapse
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Israeli Minister Yoav Gallant said that it is "a clear and unequivocal statement" that "we want Assad to fall" and be replaced by a more moderate regime, after the United States announced the discovery of a crematorium in Syria.
Addressing reporters on Monday, Jones said the Kremlin has assisted in years of mass murders and other atrocities including chemical attacks and hospital bombings on civilians and rebel forces alike. More so, the State Department said some 50 detainees a day are being hanged at Saydnaya military prison.
"The time has come for the world - chiefly the United States - to act to halt these human rights violations".
Meslet, in Geneva for the United Nations -mediated talks, told Saudi-owned TV station al-Hadath that the government was known to move prisoners around from site to site for interrogations and, in some instances, executions.
Amnesty's report accused the Syrian government of carrying out a "policy of extermination" at Saydnaya by repeatedly torturing detainees and withholding food, water, and medical care.
Along with the crematorium accusations, the source referred to the allegations of the government's use of "barrel bombs" and "chemical weapons" as calculated fabrications.