DAMASCUS, July 19: Rebels battled deep into Damascus and seized control of parts of Syria’s borders on Thursday, pressing on with their advance after the assassination of Bashar Al Assad’s top security officials brought their 16-month uprising to a head.

Government forces unleashed helicopter gunships and artillery against their own capital. Damascus residents told of buildings in flames and corpses in the streets.

Diplomatic efforts — clearly overtaken by events on the ground — collapsed in disarray when Russia and China vetoed a UN Security Council resolution that would have imposed sanctions on Syrian authorities. Washington said the Council had ‘failed utterly’.

The next few days will be critical in determining whether Mr Assad’s government can recover from the blow of Wednesday’s bombing, which wiped out much of Mr Assad’s command structure and wrecked his inner circle’s aura of invulnerability.

The attack on a crisis meeting inside a security headquarters killed Mr Assad’s powerful brother-in-law, his defence minister and a top general. The head of intelligence and the interior minister were wounded and their condition is not clear.

Mr Assad’s own failure to appear in public for more than 24 hours – he was finally shown on television on Thursday afternoon swearing in a replacement for his slain defence minister – added to the sense of his power evaporating.

Rebels claimed control of the main border crossing with Iraq on the Baghdad-Damascus highway at Abu Kamal – one of the most important trade routes in the Middle East – and at least two crossings with Turkey, at Jarablus and Bab Al Hawa.Lorries were queued up at Bab Al Hawa, a major commercial crossing, shut while battles raged nearby. Footage which rebels said was filmed at the checkpoint showed them climbing onto rooftops and tearing up a poster of Mr Assad.

“The crossing is under our control. They withdrew their armoured vehicles,” said a rebel fighter who would only be identified as Ali, being treated for wounds on the Turkish side.

Damascus residents said a heavy onslaught of security force shelling and firing from helicopters went on through the night and continued on Thursday. Some reported explosions in the capital’s troubled northeastern and southern districts.

A woman who visited the neighbourhood of Tadamon, the scene of heavy fighting, said a police station was destroyed.

“I saw five charred bodies strewn across the street,” she told Reuters by telephone. “Seven police cars were torched ...some mosques in Damascus are calling on loudspeakers which shelters are available for people who have fled.”

A witness said rebels attacked the main police headquarters in Damascus. “Gunfire has been intense for the past hour. It is now dying down but the streets around the police command remain empty,” said a resident of Qanawat, an old central district where the Damascus Province police headquarters is located.

Other parts of the city were paralysed.

Homes and shops were shuttered as Damascenes feared violence. Officials in neighbouring Lebanon said refugees were pouring across the frontier: a security source said 20,000 Syrians had crossed.

“Everyone is looking now at how well Assad can maintain the command structure. The killings yesterday were a huge blow, but not fatal,” said a western diplomat following Syria.—Reuters