Transcript for US State Department accuses the Syrian government of new war crimes

way here. Another harrow emerging from the war in Syria. The U.S. Department accusing the Syria carrying out mass executions. U.S. Officials say they uncoveree atrocity using satellite images of a notorious prison outside of Damascus. ABC's Martha Raddatz. Reporter: Tonight, new horrors revealed in these satellite images. A secret crematorium constructed in the notorious sednaya prison north of Damascus, where as many as 50 people are killed every day. Look at the nearby buildings in the complex, a white blanket of snow covers them, but the roof of this building, with the intense heat from within, snow free. That is where the state department believes the bodies are burned, to hide evidence of an estimated 5,000 to 15,000 political killings. The building of a crematorium is an effort to cover up the extent of mass murders taking place in sednaya prison. Reporter: The evidence of the crematorium is circumstantial, no images exist from inside the prison. But amnesty international has recreated the prison itself, based on interviews with those who managed to survive the conditions. "As we arrived," this man, every guard grabbed a detainee and started beating them." The U.S. Blames Assad for the crematorium, but says Russia and Iran have played a part, for supporting the regime. A regime the U.S. Attacked just last month after evidence emerged it used chemical weapons to attack civilians. Martha, this new evidence as the president prepares for his first overtrip to Saudi Arabia, Israel and Italy. He'll meet with Sunni leaders. They'll be shown these satellite images. All those groups already did despised the Assad regime. They'll be very happy about this tough stand against them. Now to another global worry at this hour.

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