Syria: Videos show ongoing air strikes on Homs countrysideIBTimes UK

At least 60,000 people have died in Syrian government jails during the five-year conflict, a monitoring group has revealed. The UK-based Syrian Observatory for Human Rights said in a statement: "No fewer than 60,000 detainees were martyred... either as a result of direct bodily torture, or denial of food and medicine."

Syrian government officials could not be reached for a comment, the Reuters agency reported, while noting that the government had rejected similar reports in the past too.

Rami Abdulrahman, the Observatory's director, said the monitoring group had arrived at the number by adding up death tolls provided by its sources in several Syrian jails and security agencies.

However, the group said it had been able to verify the deaths of 14,456 people, including 110 minors, since the beginning of the Syrian civil war in 2011. Besides, more than 20,000 people have reportedly died at Sednaya prison near Damascus, Abdulrahman added.

According to the London-based observatory group's Facebook statement, the information came from "reliable sources within the regime's security branches, most importantly the Air Force Intelligence and State Security, in addition to reliable sources in Sednaya military prison".

Earlier in February, UN investigators had said the detainees held by the Syrian government were being killed on a massive scale, which amounts to a crime against humanity.

"We know a large numbers of people have died in detention in Syria. The only way to get to the bottom of the numbers question is to allow for independent monitors into the detention centres," Nadim Houry of the Human Rights Watch (HRW) group told the news agency. However, the HRW said it could not verify the Observatory's statistics.

Syrian Prison
Fighters from the Democratic Forces of Syria inspect a prison which, according to them, belonged to Islamic State fighters in al-Shadadi town in Hasaka province, Syria, on 26 February 2016REUTERS/Rodi Said

In a report published by the HRW in December, it said a Syrian defector — known as Caesar – smuggled out tens of thousands of photographs taken between May 2011 and August 2013, documenting more than 28,000 deaths in government custody, suggesting the government had violated humanitarian rights.

The HRW said a group formed by an opposition body called the Syrian Association for Missing and Conscience Detainees calculated the toll and reviewed all the photos. However, Syrian President Bashar al-Assad had dismissed the Caesar photos as "allegations without evidence" and part of a Qatar-funded plot against his government.