Major General Robert Mood, chief of a UN observer mission in Syria, visited the site of two powerful blasts that rocked Damascus on Thursday, an AFP correspondent reported.

Mood surveyed the damage left by the explosions that took place during morning rush hour on a highway south of the capital.

The attacks came a day after the Norwegian general escaped unharmed when a roadside bomb exploded as he led a team of UN observers into the southern flashpoint city of Daraa.

Six Syrian soldiers escorting them were reportedly hurt in Wednesday's bombing.

The blasts come despite a UN-backed ceasefire that went into effect on April 12 with the aim of ending 14 months of bloodshed in Syria.

The Syrian Observatory for Human Rights said Thursday's blasts targetted a security building.