Sounds of gunfire were heard in Damascus on Saturday night, amid growing speculation about a coup attempt.
The Syrian state television network (SANA) stopped broadcasting on Saturday night, and the news agency's websites were inaccessible in Arabic and English.
Explosions and gunfire were heard near the general headquarters building and the government communications building in the capital.
Local sources said that Brigadier General Hossam Louka, the head of the regime's internal security services, tried to overthrow President Bashar Al-Assad, who was out of the country on Saturday.
A Russian military plane landed at Damascus International Airport on Saturday evening, amid growing speculation that Assad was on board and returning from meetings in Moscow.
Unconfirmed reports also claimed that Assad had been moved to a safe house in the wake of the coup attempt.
There were reports of clashes between soldiers of the Syrian Republican Guard Division and soldiers of the Syrian Army's 4th Division under the command of Major General Maher al-Assad, the president's brother, in the Susa village area of Damascus, with shooting at several government buildings.