Human Rights Watch said Thursday that the ouster of president Bashar al-Assad has created an opportunity for Syria to "turn the page" on decades of repression and lead by example on human rights.
More than half a century of brutal rule by the Assad clan came to a sudden end on the weekend after a lightning rebel offensive swept across Syria and took the capital Damascus.
Assad's ouster "has created a momentous opportunity for Syria to break with decades of repression and turn the page on human rights," Human Rights Watch (HRW) said in a statement.
"A better future for Syria requires addressing decades of abuse by the former government and other warring parties during the country's 13-year conflict... and protecting Syrians regardless of their ethnic or sectarian backgrounds or political affiliations."
The group noted that the Islamist Hayat Tahrir al-Sham (HTS) and the other rebel organisations behind the offensive were "also responsible for human rights abuses and war crimes".
HTS is rooted in Syria's branch of Al-Qaeda and is proscribed as a terrorist organisation by many Western governments, though has sought to moderate its rhetoric.
There has been concern in the West about how the country's new rulers will treat Syria's many religious and ethnic minority groups.
New interim prime minister Mohammad al-Bashir sought to assuage these fears on Wednesday, saying that "we will guarantee the rights of all people and all sects in Syria".
HRW called on Syria's leadership to use this "unprecedented opportunity to lead by example on human rights".
"This is a critical moment to reject the horror show of the past," the rights group's Middle East director Lama Fakih said.
The group also said the United States, European Union and others should urgently consider lifting some sanctions which have been documented to have had a "negative impact" on humanitarian operations in Syria.
It also said countries which host a sizeable number of Syrian refugees "should not rush to deport or otherwise expel Syrians".
Austria has already announced that it wants to deport refugees who fled the civil war back to Syria, while several other countries have frozen asylum requests.
"Forcibly expelling refugees or pressuring to them to return at this juncture would risk compounding the humanitarian crisis," Human Rights Watch said.
Syria's civil war, which began in 2011 after the Assad government brutally suppressed pro-democracy protests, killed 500,000 people and displaced half the country.