Syria’s deputy foreign minister, Faisal Mekdad, said none of the observers had been wounded in the blast, state TV reported. “This was a criminal act aimed at distorting Syria’s image,” it quoted him as saying.

The target was not immediately clear. The area is home to the Syrian army officers club and a building belonging to the ruling Baath Party and is also not far from the army command, according to Al Jazeera. 

Meanwhile, the rebel Free Syrian Army claimed a bomb attack in the heart of Damascus on Wednesday that it said targeted an operational meeting in a local military headquarters, according to AFP.

“The FSA operation targeted a military command office with explosives designed to go off at a meeting of army officers and members of the shabiha (pro-government militia) which decides on daily operations in Damascus,” Maher Nuwaimi, head of the FSA coordination command in Syria said.

Damascus has been rocked by several bomb blasts recently, including an attack last month at the national security building that killed three of President Bashar al-Assad’s regime members including his borther-in-law.

The latest violence comes as some Islamic countries prepare to meet in the Saudi city of Mecca to discuss the crisis. The Organisation of Islamic Co-operation is expected to suspend Syria’s membership, despite objections from Iran, Syria’s last regional ally

More than 23,000 people have been killed in violence in Syria since the outbreak of a revolt in March last year, the UK-based Syrian Observatory for Human Rights said on Tuesday.