The Syrian government has "categorically" denied US accusations of mass killings at a prison near Damascus, including executing political opponents and burning the victims in a crematorium at the site.

The allegations are "a new Hollywood plot" to justify US intervention in Syria, the foreign ministry said in a statement on Tuesday.

It described the accusations made a day earlier by the US state department as "lies" and "fabrications", noting what it called a US track record of making false claims as a pretext for military aggression.

The state department said on Monday that it believes about 50 detainees are being hanged each day at the Saydnaya military prison, about 45 minutes' drive north of Damascus.

Many of the bodies are then burned in the crematorium "to cover up the extent of mass murders taking place," said Stuart Jones, the top US diplomat for the Middle East.

Speaking on Monday, Sean Spicer, the White House press secretary, said the "Assad regime has sunk to a new level of depravity" and that it had done so "with seemingly unconditional support from Russia and Iran".

The allegations of mass killings came as President Donald Trump weighs options in Syria, where the US launched cruise missiles on a government air base last month after accusing Assad's military of killing scores of civilians with a sarin-like nerve agent.

The latest accusations have cast a shadow over Syria talks in Geneva, where Syrian government and opposition representatives sat down separately with the UN envoy.

Al Jazeera's Mohammed Jamjoom, reporting from Geneva, said diplomats involved in what is now the sixth round of UN-brokered Syria talks have "never been this sceptical this early on in the game".

The negotiations are focused on finding a political solution to Syria's war, now in its seventh year, and will concentrate on four separate areas, or "baskets" of issues: governance, a new constitution, elections and combating "terrorism".

Infographic: Syria's besieged communities

Diplomats involved in the talks told Al Jazeera that Staffan de Mistura, the UN's Syria envoy, and the Russian ambassador in Geneva were trying to convince parties involved in the talks to focus on "the counterterrorism issue as well as the drafting of a new constitution, and to put the other two issues on the back burner, so that at least some progress can be made", our correspondent said.

“One of the reasons diplomats are so sceptical at this point is that they don't know what exactly the US is doing with regards to this process ... there is no clear or coherent strategy from the US regarding Syria, and if the US is not engaged fully in these talks, nothing tangible can be achieved."

Syria's foreign ministry said on Tuesday that the "US administration's accusations against the Syrian government of a so-called crematorium in Saydnaya prison, in addition to the broken record about the use of barrel bombs and chemical weapons, are categorically false".

The allegation could test the Trump administration's willingness to respond to atrocities other than chemical weapons attacks that the US blames on Assad's government.

Evidence of killings

Western monitors and watchdog groups say they have accumulated evidence of mass killings in Syrian government prisons, though there have not been any substantiated allegations so far of the use of a crematorium.

The state department released commercial satellite photographs showing what it described as a building in the prison complex that was modified to support the crematorium.

The photographs, taken over the course of several years, beginning in 2013, do not prove the building is a crematorium but show construction consistent with such use.

READ MORE: Low expectations as Syria talks resume in Geneva

The revelations echoed a February report by Amnesty International that said Syria's military police hanged as many as 13,000 people in four years before carting out bodies by the truckload for burial in mass graves.

The head of the Syrian opposition delegation in Geneva welcomed the US accusations, but complained they had come too late.



"This is but a drop in the ocean. What happens in the regime's prisons is much uglier than this," Nasr al-Hariri said.