Human rights groups have launched a new campaign to free Syrian activists held by the government or rebels as they mark the third anniversary of the arrest of prominent lawyer Mazen Darwish.
The "Hearts in our Hands" campaign is intended to draw attention to the plight of thousands of Syrians, particularly journalists, medics and lawyers, who have disappeared in the conflict.
Among them is Darwish, who was arrested on February 16, 2012 along with Hani Zaitani and Hussein Ghreir, his colleagues at the Syrian Centre for Media and Freedom of Expression (SCM).
The men, like many other activists, face accusations of activities including "monitoring online news and publishing the names of the dead and disappeared," rights groups say.
The campaign urges supporters to tweet messages calling for the release of Darwish and other prisoners with the hashtag #freeSYvoices.
The groups involved in the campaign, who include Human Rights Watch, Amnesty International and Syrian NGOs like the Violations Documentation Centre, will also be researching and documenting forced disappearances of activists and civilians.
Darwish's wife, Yara Bader, said the loss of her husband and other peaceful activists had robbed Syria of non-violent discourse.
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"More than the personal, it is for our homeland, Syria, that this is the biggest loss," she said in a statement issued by the campaign.
"What Mazen and others who suffer the same fate were trying to do was to make real change in Syria through nonviolent means, recognising the dignity of all.
"By locking away these people, the regime has ensured that the only space available in Syria is for brutality, violence, and inhumanity on a large scale."
Last June, Syrian President Bashar al-Assad issued a broad amnesty that was expected to extend to thousands of prisoners, including Darwish and other peaceful activists.
But despite some releases, he and other prominent rights activists have remained in jail.
An estimated 100,000 people have been arrested by the Syrian government since an uprising began in March 2011, with some 50,000 thought to be held in security services facilities.
Rebel groups have also seized thousands of Syrians, including prominent activists Razan Zeitouneh, Wael Hamada, Samira Khalil and Nazem al-Hamadi.
The four activists were abducted in December 2013 in the rebel-held area of Douma, outside Damascus, and have not been heard from since.
Zeitouneh, an award-winning lawyer, had received threats from both the regime and armed opposition groups before she went missing.