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.
Jumaa Ibrahim and his wife Hasnaa Karam, a Syrian couple in their early 60s, arrived in Mecca on Friday, and headed straight to Islam's holiest site, the cube-shaped Kaaba.
Ending the conflict in Syria and Iraq is key to solving the migrant crisis facing Europe, a senior US official tells the BBC.
Germany is to introduce some form of border controls with Austria, German and Austrian media report, as thousands more migrants arrive this weekend.
The number of migrants entering Hungary from Serbia hit a new record on amid tension in eastern Europe over how to deal with the crisis.
Two Russian cargo planes carrying 80 tonnes of humanitarian aid have landed in Syria, Syrian state media say.
France suspends the country's honorary consul in the Turkish port of Bodrum after a television report showed dinghies being sold to migrants from a shop that she owned.
Dozens of Syrian government troops and Islamic State fighters have been killed in fighting around a government-held air base in eastern Syria in a region that is a stronghold for the jihadists, a monitoring group said on Thursday,
US and Nato express concern over reports that Russia is increasing its military presence in Syria.
A Hungarian camerawoman is fired after shocking footage emerged of her intentionally tripping refugees fleeing police near the country's border as she covered the crisis for a local news outlet.
European Commission President Jean-Claude Juncker has announced plans that he says will offer a "swift, determined and comprehensive" response to Europe's migrant crisis.
