A suicide car bomb killed at least 15 people and wounded 53 in the main business district of Damascus yesterday in what the Syrian prime minister said was a response to army gains against rebels around the capital.

The bomb near a school in the Sabaa Bahrat district, which also houses the Central Bank and Finance Ministry, set cars ablaze and damaged buildings, state television footage showed.

A Damascus resident who described the blast as the biggest she had heard in the capital during the two-year-old revolt against President Bashar al-Assad said large plumes of black smoke were rising from the Sabaa Bahrat district.

Car bombs and attacks on civilians are commonplace in the Syrian conflict, which the United Nations estimates has killed more than 70,000 people, without so far producing a winner.

Each side has accused the other of using chemical weapons, among other breaches of international law, although it remains unproven whether such weapons have actually been fired.

UN Secretary-General Ban Ki-moon said an advance team of experts had gone to Cyprus and was awaiting permission from the Syrian government to investigate the conflicting assertions. After the car bomb blast, Syrian TV showed footage of seven bodies in the street, including at least two charred corpses in the wreckage of an overturned bus.

Other vehicles were still on fire, lined up in what appeared to be a car park.

A woman with a blood-covered face was carried away on a stretcher. Panic-stricken women in black dresses and headscarves ran to-wards the scene. Children in school uniform were shown in bandages.

The state TV presenter described the attack as unprecedented and said: “We only have one choice, either win or die.”

There was no immediate claim of responsibility for the attack, but each side blamed the other.

Russia said the blast occurred about a kilometre from the Russian embassy and that Moscow “decisively condemns the latest cruel foray by terrorists whose criminal activity is killing and causing suffering among peaceful people”.

A Russian Foreign Ministry statement said the bombing was the second major “terrorist act” near the embassy in about six weeks, “which creates a real danger to the lives and security of its employees”.

It said “extremist groups in Syria that resort to terrorist explosions and mortar attacks on residential areas must receive a consolidated and uncompromising rebuff from the international community”.

Syrian insurgents based in the outskirts of Damascus have pushed into areas near the government-held heart of the city, stepping up mortar and car bomb attacks in recent weeks. But rebels said the army had intensified attacks on villages in the rebel-held Ghouta area to the east of the city since mid-March, besieging some of them under siege to pin rebels back.

“The entrance of Ghouta from the north is under siege,” said a rebel commander in the area. The military, he said, was trying to disrupt rebel preparations for a “big battle” to break into central Damascus, the seat of Assad’s power.

Osama al-Shami, an activist from southern Damascus, said Assad’s forces had launched a big tank-led assault on eastern Ghouta from the side of the International Airport to the south.

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