GENEVA (Reuters) - Syrian activists say they have given U.N. investigators evidence of alleged war crimes committed by Russia and Iranian-backed militia in the battle for the Syrian city of Aleppo, calling for them to face justice for killing civilians and other atrocities.

A general view shows damaged buildings in Aleppo city at night April 11, 2015. REUTERS/Rami Zayat - RTR4WWOK

The United Nations Commission of Inquiry (COI) on Syria, which began collecting testimony and evidence five years ago for future prosecutions, has already shared some confidential files with national authorities pursuing foreign fighters.

Fadel Abdul Ghany, head of the Syrian Network for Human Rights, and Husam Alkatlaby, director of the Violations Documentation Center, met U.N. investigators on Wednesday to press the case for probing crimes committed during the long siege and recapture of rebel-held eastern Aleppo last month.

Syria, and its allies Russia, have dismissed accusations of abuses or war crimes.

Abdul Ghany said activists “found a similarity between the violations committed by the Russians and the regime, and sometimes the Russians exceed the regime in some kinds of violations”.

“We recorded the killing of 1,305 civilians at the hands of Russian forces,” he told Reuters, referring to victims of hundreds of Russian air strikes between July and December 2016. Roughly one-third of fatalities were children.

“All incidents we provided are violations of IHL (international humanitarian law). Lots of them amount to war crimes, especially targeting the vital civilian centers, especially when we are speaking about hospitals.”

After months of bombardment and a final few weeks of intense air strikes and Syrian army advances on the besieged part of Aleppo, a local ceasefire was reached on Dec 15 which allowed tens of thousands of civilians and fighters to leave.

“The Russian air force was trying to target specific points, for example hospitals, schools or whatever. They fly at higher altitude (than the Syrian air force) - this comes through in the testimonies, the interviews,” Alkatlaby said.

Since the Russian air campaign began on Sept 30, 2015, Russian forces have killed “a minimum” of 4,000 Syrians in all, Abdul Ghany said. “We have all documented, by name, details, date, photos.”

“IRAN’S COMPLICITY”

The activists, joined by the “White Helmets” civil defense teams and the Independent Doctors Association, documented 31 cluster munition attacks in Aleppo by Russian forces and three by Syrian government forces, as well as their use of banned incendiary weapons, Abdul Ghany said.

Syria’s government rejects accusations it has carried out abuses, denying reports of torture and extrajudicial killings, the targeting of civilians and use of chemical and incendiary weapons and improvised munitions known as barrel bombs.

Russia says it only bombs militants, and that accusations of war crimes against it are part of a Western-backed propaganda campaign. Defense Ministry spokesman Major-General Igor Konashenkov has said the White Helmets organization is close to the jihadist group formerly known as the Nusra Front.

“There is clear evidence that the attacks by Russia on Syrian civilians constitute war crimes,” the four groups said in a joint letter to the COI’s chairman Paulo Pinheiro, whose team is expected to issue a report on Aleppo in February.

“We also urge the Commission to explore fully all credible accounts of Iran’s complicity in war crimes in Aleppo,” it said, citing the “central role” of Iranian-backed militias in enforcing the siege and preventing civilians from fleeing.

Iran, which has backed President Bashar al-Assad with weapons, oil shipments and military advisers, denies any involvement in killing of civilians and emphasizes Tehran’s determination to support Assad in his “fight against terrorism”.

Abdul Ghany said a special tribunal should be set up to try war crimes, since Russia would veto attempts to send the issue to the International Criminal Court.

“Now we need from the COI to push forward toward this mechanism in order to prosecute the perpetrators. Otherwise there is no meaning for all of this documentation work.”