The head of the Democratic Front for the Liberation of Palestine was lightly injured on Thursday in a car bomb that shook central Damascus and killed several people, a DFLP official said.

Nayef Hawatmeh, 74, suffered minor injuries but did not require hospital treatment when the bomb exploded near DFLP offices in Syria, DFLP central committee member Khalid Atta told Ma'an.

Atta said the bomb had not targeted the DFLP office, which was damaged in the attack.

Palestinian ambassador to Syria Mahmud al-Khadi said the explosion also damaged the Palestinian embassy in Damascus. He reiterated that Palestine would not be drawn into the conflict in Syria and said efforts were underway to remove armed insurgents from Palestinian refugee camps.

The Britain-based Syrian Observatory for Human Rights said at least 31 people were killed in the blast, which occurred near an office of President Bashar Assad's ruling Baath Party. It said most of those killed were civilians, though the death toll included security forces.

Other activists said 40 people were killed, including children, and 70 people were wounded.

Television footage showed at least four bodies strewn across the street after the blast, which state media blamed on what it described as a suicide bombing by "terrorists" battling Assad.

Central Damascus has been relatively insulated from the nearly two-year conflict which has killed around 70,000 people across the country, according to the United Nations.

But rebels who control districts to the south and east of the capital have been attacking Assad's power base for nearly a month, and have struck with devastating bombings several times in the last year.

Al Qaeda-linked rebel group Jabhat al-Nusra has claimed responsibility for several of those attacks.

Thursday's blast, which activists said was followed by at least three other explosions elsewhere in Damascus, sent a pall of black smoke billowing into the sky above the Mazraa district.

Russia's Itar-Tass news agency quoted a diplomat as saying the blast blew out windows at the Russian Embassy compound, which faces on to the road where the bomber struck, but no employees were wounded.

"The building has really been damaged... The windows are shattered," the diplomat said.

A correspondent for Syrian state television said he saw seven body bags with corpses in them at the scene. He said he counted 17 burnt-out cars and another 40 that were destroyed or badly damaged by the force of the blast, which ripped a crater 1.5 meters deep into the road.

The official SANA news agency said casualties included children at a nearby school in Mazraa, which it described as a busy residential district of the capital.

Activists reported at least two further blasts in the city after the Mazraa explosion. The Observatory said two car bombs exploded outside security centers in the north-eastern district of Barzeh, but there were no details of casualties.

Syrian TV said security forces had detained a would-be suicide bomber with five bombs in his car, one of them weighing 300 kg.