Rebel leader Ahmed al-Sharaa, also known as Abu Mohammed al-Jolani, also said he would dissolve the security forces of the former regime, in a statement seen by the Reuters news agency.

Videos showing thousands of prisoners being freed from Saydnaya prison – referred to as a “human slaughterhouse” by rights groups – surfaced after the collapse of the Assad government on Sunday.

Almost 60,000 people were tortured and killed in the prisons run by Assad, UK-based monitoring group Syrian Observatory for Human Rights said.

Jolani’s Islamist militant group, Hayat Tahrir al-Sham (HTS), led other Syrian rebel factions in a lightning offensive that toppled the Assad dynasty’s 54-year-rule.

Assad fled to Russia in the early hours of Sunday, where he and his family have been given asylum, after rebels captured the capital Damascus.

In a separate statement, Jolani said pardons for those who took part in the torture or killing of prisoners were out of the question.

“We will pursue them in Syria, and we ask countries to hand over those who fled so we can achieve justice,” he said.

Since the fall of President Bashar al-Assad Syrians have rushed to the regime’s infamous prisons, desperately searching for their loved ones. In a 2022 report, the Turkey-based Association of Detainees and The Missing in Saydnaya Prison (ADMSP) said Saydnaya “effectively became a death camp” after the start of the civil war in 2011.

Jolani also said he would dissolve the former Assad regime’s security forces. It is not clear how quickly they could be reconstituted by rebel fighters amid concerns about Israeli strikes on the country’s military infrastructure.

In the statement seen by Reuters, Jolani said his group was working with international organisations to secure possible chemical weapons sites.

When asked about the Reuters report, Deputy Pentagon Press Secretary Sabrina Singh said the US “welcomed” Jolani’s words but said they needed to be met with actions.

“Our focus is that these chemical weapons do not fall into the wrong hands”, she added.

This comes after Israel carried out hundreds of strikes across Syria and seized a number of military assets.

One of the attacks targeted a research centre with suspected links to chemical weapon production, according to local media reports.

Israel says it is acting to stop weapons falling “into the hands of extremists”.

A chemical weapon is described by the UN’s chemical watchdog, the Organisation for the Prohibition of Chemical Weapons (OPCW), as a chemical used to cause intentional death or harm through its toxic properties.

Their use is prohibited under international humanitarian law.

Between 2013 to 2018, Human Rights Watch documented at least 85 chemical weapons attacks in Syria, accusing the ousted government of being responsible for most of them.

Assad’s government denied ever using chemical weapons.Syria signed the OPCW’s Chemical Weapons Certificate in 2013, a month after a chemical weapons attack on suburbs of Damascus left more than 1,400 people dead.

It is not known how many chemical weapons Syria has, but it’s believed Assad kept stockpiles and that the declaration he had made was incomplete.

Victims of chemical attacks in Syria have recently spoken to the BBC about the devastating impacts they’ve experienced.

Meanwhile, European foreign ministers are meeting in Berlin on Thursday to hold critical talks on Syria and Ukraine.

A day later, leaders of the G7 countries will also discuss the latest developments in Syria at a virtual meeting, the White House said.