With 5,000 dead and thousands more detained and "disappeared", Syrian President Bashar al-Assad is presiding over the most brutal anti-democratic crackdown of the Arab spring. Today we reveal a shocking new dimension to his ruthless assault on peaceful protesters: systematic abuse of the country's medics, hospitals, and ambulances.

Assad's militias have been detaining and torturing medical personnel and abusing Red Crescent facilities: snatching wounded citizens from hospitals and shooting at and from ambulances. These are crimes under international law. Given this new evidence, how can states like Russia and China continue to protect Assad and his murderous regime?

Targeting doctors

Dr Maaz Fares was the director of the national hospital in al-Houla, a town in the flashpoint of Homs. He was also the local secretary of the Red Crescent (the Muslim world's affiliate of the Red Cross).

In August, government forces arrested Dr Fares at a checkpoint for transporting medical supplies. Three months later his body was delivered to his family. He clearly died in detention, but family members told us they were forced to sign a gag agreement saying he'd died of a heart attack.

Dr Fares is not alone. Dr Ibrahim Othman, the 26-year-old co-founder of Damascus Doctors a pressure group of medical professionals, was shot dead while escaping to Turkey. A YouTube video, uploaded this weekend, shows the dead doctor and photos of his passport. Mourners described Dr Othman as "strong and fearless, with a pure heart".

According to our interviews with Red Crescent volunteers and our network of 50 citizen journalists across Syria, Assad's forces have detained at least 13 more doctors and threatened them with torture for attending to wounded protesters. As a former Red Crescent volunteer told us:

They arrest us every Friday for treating protesters. One time they locked us up for 12 hours. They took some of our group to the basement of the police station and forced them to take off their clothes – carrying the Red Crescent emblem – and shoes, before blindfolding them. We could hear the screams as they were tortured.

Horror hospitals

In addition to targeting doctors and nurses, Syrian paramilitaries have also gone after the wounded. At least 57 patients have been taken from hospitals in Latakia and Homs, including 16 from a Red Crescent facility. Avaaz continues to work to pressure Assad into releasing these and the thousands of other disappeared. Rose al-Hamsi, from Homs, who escaped from Syria last month, told us:

Injured protesters are entering hospitals with a leg wound and leaving in a body bag with a bullet between their eyes. Most injured protesters cannot get treatment, as the Shabiha death squads are situated in the hospitals and are regularly executing people they suspect are protesters.

The government's non-uniformed Shabiha militias have set up shop in some hospitals, and eyewitnesses report killings of wounded protesters. Bisan Othman, a Red Crescent volunteer from Homs, said:

One man was actually undergoing surgery in the operating room and they came and tore the oxygen mask away and took him. He died.

We've also received seven videos showing the death squads using Red Crescent ambulances to fire on and kidnap protesters – including an ambulance used as a sniper's gun platform and a paramedic shot in his vehicle. In one case, paramilitaries in Homs used an ambulance to fire at protesting school children.

Take action: After 5,000 deaths, the Assad regime is increasingly isolated. Even the normally conservative Arab League has imposed serious sanctions. Russia is now one of Assad's last sponsors – providing weapons and money to fuel the brutality – yet hasn't received much international criticism. Hundreds of thousands of us are now calling on Russia to stop supporting the carnage. Let's keep up the pressure. Sign our petition.

Avaaz has a courageous ground-team working in Syria and neighbouring countries. Our goal is to document the country's violence with the highest possible accuracy, by verifying facts and gathering eyewitness accounts.