A Syrian free speech activist and open software developer was executed by the regime of Bashar al-Assad, according to new reports.

Syrian free speech activist and open software developer Bassel Kharabil was executed by the regime of Bashar al-Assad, The Jimmy Wales Foundation reported on Tuesday.

"Today we received the horrific news that Bassel was executed immediately after his disappearance nearly two years ago," the charity established by the founder of Wikipedia said.

Kharabil was a defender of information freedom who was detained by Syria's military intelligence agency in March 2012 for supporting the popular uprising against the Assad regime.

In October 2015, authorities moved him from Adra central prison on the outskirts of Damascus to an undisclosed location.

His family at the time feared that he had been tried and sentenced to death by a military court in Damascus.

On Tuesday, digital activism community Global Voices paid homage to Kharabil.

"We are deeply saddened to learn about the death of our friend Bassel Khartabil. We mourn his loss and send our deepest condolences to his family, friends and all those who knew and loved him," it said in a statement.

Khartabil was the founder of Creative Commons Syria, a non-profit organisation that helps people share artistic and other work using free legal tools.

The Palestinian-Syrian also began creating photographic three-dimensional models of the ancient city of Palmyra, which has partially been destroyed by the Islamic State group.

In October, as part of the New Palmyra Project, a group of activists released an online collection of reconstructed models of the ancient city based on photographs taken by Kharabil in a number of visits to the site.

More than 330,000 people have been killed in Syria since war broke out in March 2011 with anti-government protests that have evolved into a complex proxy war.