No group has claimed the four activists' abduction and they have not been heard from since.
Ankara-backed rebels played a key role in supporting Sharaa's Islamist group Hayat Tahrir al-Sham (HTS), which headed a rebel alliance that seized Damascus on December 8, toppling longtime ruler Bashar al-Assad.
The seismic change in Syria is expected to yield deeper Turkish sway just as a change of US administration is raising questions over how long Washington will keep backing the country's Kurdish-led forces.
Assad fled Syria following a lightning offensive spearheaded by the Islamist Hayat Tahrir al-Sham (HTS), more than 13 years after his crackdown on democracy protests precipitated one of the deadliest wars of the century.
Darwish was detained for months by one of the most feared branches of the former government's many-tentacled intelligence services.
Syrians will not miss Assad, a brutal ruler who failed his people.
The offensive, which took just 10 days to sweep across Syria and take the capital Damascus, stunned the world and brought an end to more than a half a century of brutal rule by the Assad clan.
"We would like to see the situation in the country stabilised somehow as soon as possible," Kremlin spokesman Dmitry Peskov told reporters.
"Their human capital, their experience will allow the country to flourish," Bashir said in an interview published Wednesday.
Three teenagers who were stopped from travelling to Syria from Turkey have been flown back to the UK and arrested, Scotland Yard has said.
The Vatican's ambassador to the United Nations endorses military action against the Islamic State group in Iraq and Syria -- an unusual move because the Vatican traditionally has opposed force in the region
Islamic State (IS) accepts pledge of allegiance from Nigeria's militant group Boko Haram, according to an audio message
Melbourne schoolboy who travelled to Middle East to fight with Islamic State (IS) dies in suicide attack in Iraq
US-led coalition air strike in Syria hits an oil refinery run by the Islamic State militant group killing 30 people
Nigerian militant group Boko Haram pledges allegiance to Islamic State (IS) via Twitter post
The military chief of Syria's al-Nusra Front militant group is killed in an air strike, says the group
Melanie Smith monitors around 90 women daily who are believed to be living with Islamic State militants in Syria and Iraq and depicts an idea into what life really is like inside IS
A former Royal Marine became the first Briton to be killed while fighting alongside Kurdish forces against Islamic State in Syria, the Kurdish militia
Nineteen of 220 members of an Assyrian Christian community kidnapped by Islamic State (IS) in Syria released
