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.
A large dust storm hits western parts of the Middle East, putting dozens of people in hospital and leading to public health warnings.
David Cameron is facing questions over the decision to carry out a drone strike in Syria which killed two British Islamic State jihadists.
The Greek government and the UN refugee agency have brought in extra staff and ships to deal with some 25,000 stranded migrants on the island of Lesbos.
David Cameron will set out details of government plans to resettle more refugees from Syria, as France says it will take 24,000.
Singer and activist Bono has offered support to refugees fleeing their homes by changing the chorus of a U2 song mid-concert to help raise awareness of their plight.
German Ambassador in Dhaka Dr Thomas Prinz today says his country will welcome political asylum-seekers but no illegal migrants.
German Chancellor Angela Merkel says the "breathtaking" flow of migrants into Germany will "occupy and change" the country in the coming years.
Austria says it is planning to phase out special measures that have allowed thousands of migrants to travel freely from Hungary to Western Europe.
A convoy of cars driven by German and Austrian activists crosses into Hungary to pick up migrants and help them reach western Europe.
US Secretary of State John Kerry expresses concern to Moscow over reports of Russian military build-up in Syria, the state department says.
