Twin bombs killed 44 people in the Old City of Damascus on Saturday, March 11, a monitoring group said, in one of the bloodiest attacks in the heart of the Syrian capital, AFP reports.

A roadside bomb detonated as a bus passed and a suicide bomber blew himself up in the Bab al-Saghir area, which houses several Shiite mausoleums that draw pilgrims from around the world, the Syrian Observatory for Human Rights said.

Several Shiite pilgrims were among the dead.

"There are also dozens of people wounded, some of them in a serious condition," Observatory chief Rami Abdel Rahman told AFP.

The director general of the capital's Al-Mujtahed hospital told AFP earlier there were at least 28 people dead and 45 wounded.

The SANA state news agency reported that "two bombs planted by terrorists exploded near the Bab al-Saghir cemetery in Bab Musalla, causing dead and wounded."

Shiite shrines are a frequent target of attack for Sunni extremists of Al-Qaeda and the Islamic State group (IS), not only in Syria but also in neighbouring Iraq.

The Sayeda Zeinab mausoleum to the south of Damascus, Syria's most visited Shiite pilgrimage site, has been hit by several deadly bombings during the six-year-old civil war.