Fourteen people were killed in the attack, one of the deadliest in the capital in years.

While the Syrian government's decade-long conflict with insurgents continues in parts of the country including the rebel-held northwest, bombings in Damascus have become exceedingly rare since President Bashar Assad's troops pushed opposition fighters from the capital's suburbs in 2018.

The explosions, which also left several wounded, happened at a busy intersection, near a main bus transfer point where commuters and schoolchildren typically converge.

After the blasts, Syrian state TV showed footage of smoke rising from a charred bus as soldiers hosed down the vehicle and onlookers flocked to a nearby bridge to watch.

No one immediately claimed responsibility for the attack, but several insurgent and jihadist groups that seek to overthrow Assad are active in Syria.

Separately, rescue workers reported 10 people were killed, including four children and their teacher, in government shelling of a town in the last rebel enclave in the country's northwest.

A further 20 were reported injured as dozens of shells hit the town of Ariha, in Idlib province.

Reports of the shelling that hit a market and roads near schools as students were heading to classes were "shocking", UN Deputy Regional Humanitarian Coordinator Mark Cutts said.

The attack was one of the most violent in the area since a March 2020 truce in the northwest negotiated by Turkey and Russia - allies of the opposition and Syrian government, respectively.

The truce has been repeatedly violated, and government forces often vow to take territories still out of their control.

In the central city of Hama, meanwhile, an explosion at an arms depot left six pro-government fighters dead, according to the Syrian Observatory for Human Rights, an opposition war monitor.

Syria's conflict began in March 2011 and has left between 350,000 and 450,000 people dead and displaced half the country's population, including 5 million who are refugees abroad.

On Wednesday, New York-based Human Rights Watch called on countries in the region and Europe hosting Syrian refugees to stop forcing them to return to the war-torn country.

"The harrowing accounts of torture, enforced disappearance, and abuse that refugees who went back to Syria endured should make it patently clear that Syria is not safe for returns," said Nadia Hardman, refugee and migrant rights researcher with HRW.

Australian Associated Press