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.
Hillary Clinton attacks her main rival Bernie Sanders on gun laws at the Democratic presidential debate.
Kurdish forces have carried out a wave of forced displacement and mass house demolitions - amounting to war crimes - in northern Syria, a rights group says.
The US military has delivered more than 45 tonnes of ammunition to rebels fighting the jihadist group Islamic State (IS) in north-eastern Syria.
Russia's air force hit 60 Islamic State targets in Syria over the past 24 hours and killed around 300 militants, the Defense Ministry says.
Plans to speed up the deportation of failed asylum seekers are to be discussed at a meeting of EU ministers in Luxembourg.
Nato defence ministers will assess the "troubling escalation of Russian military activities" in Syria, the alliance's secretary-general says, ahead of talks in Brussels.
Russia says it has launched rocket strikes on Islamic State group targets in Syria from warships in the Caspian Sea - about 1,500km (930 miles) away.
At last Russia has decided that it will not be in the sidelines any more. After much speculation among western powers about its role in the four-year long Syrian war, Russia has come out full force to defend its long time regional ally, President Assad.
Islamic State militants in northern Syria have blown up another monument in the ancient city of Palmyra, officials and local sources say.
Putin's action is a clear message to the West that Russia is a world power to be reckoned with. He is ready to use his military power to back his diplomatic goals. He is also sending a message to the West to not meddle with Russia over Ukraine.
