A suicide bomber detonated a car packed with explosives on Monday in a busy residential and financial district of central Damascus, killing at least 15 people, setting cars and buildings on fire and sending plumes of black smoke over the capital, Syrian state-run media said.

The explosion came as UN chief Ban Ki-moon said inspectors were ready to deploy to Syria within 24 hours to investigate reports of chemical weapon attacks, but have not yet received permission from President Bashar al-Assad's government.

The blast, described by state-run Syrian TV as a terrorist suicide bombing, occurred near Sabaa Bahrat Square, one of the capital's biggest roundabouts. The Syrian central bank, the Finance Ministry and state-run investment agency, a mosque and a school are located nearby.

The explosion also wounded at least 53 people, according to Syrian state TV.

It was the latest in a series of car bombs and suicide bombings to hit the Syrian capital in recent months. The two-year civil war, which the UN says has killed more than 70,000 people, has become increasingly chaotic as rebels press closer to Assad's seat of power in Damascus after seizing large areas in northern and eastern parts of the country.

TV images showed thick black smoke billowing from a wide street with several cars on fire. At least six bodies were seen lying on the pavement. Paramedics carried a young woman lying on a stretcher, her face bloodied, into an ambulance.

Shaken teenage students holding their backpacks were seen walking away. The blast occurred some 20 metres from the Bukhari School.

Among the buildings damaged was the state-run Syrian Investment Agency. Several cars in the building's parking lot were set ablaze in the explosion. Witnesses said a suicide attacker tried to storm the building with his vehicle but was stopped by guards. He then detonated his explosives outside the building.