BEIRUT/AMMAN - Mystery surrounded the whereabouts of Syrian President Bashar al-Assad on Thursday, a day after a bomber killed and wounded his security chiefs and rebels closed in on the centre of Damascus, vowing to "liberate" the capital.
The Syrian leader made no public appearance and no statement after a bomber killed his powerful brother-in-law, his defence minister and a top general.
By the early hours of Thursday, residents had reported no let-up in the heaviest fighting to hit the capital in a 16-month revolt against Assad's rule.
The fighting came within sight of the presidential palace, near the security headquarters where the bomber struck a crisis meeting of defence and security chiefs.
Assad's brother-in-law Assef Shawkat, a top commander and one of the pillars of the Assad clan's rule, was killed in the blast along with Defence Minister Daoud Rajha.
Another senior general also was killed and the heads of intelligence and the Interior Ministry were wounded, deeply damaging the security apparatus of the Assad family, which has ruled the country with an iron fist for four decades.
Intense clashes were reported in the capital's central districts of Mezze and Kafar Souseh, while a police station in the Hajar al-Aswad district was in flames.
The army was shelling its own capital from the surrounding mountains as night fell. Government troops, having vowed retaliation for the assassination, fired machineguns into the city from helicopters.
A security source said the bomber who struck inside the security headquarters was a bodyguard entrusted with protecting the closest members of Assad's circle. State television said it was a suicide bomber. Anti-Assad groups claimed responsibility.
Washington, which fears a spillover into neighbouring states, said the situation seemed to be spinning out of control. Russian Foreign Minister Sergei Lavrov said "the decisive fight" was under way in Damascus.
The UN Security Council put off a scheduled vote on a Syria resolution and US President Barack Obama phoned President Vladimir Putin of Russia, Assad's main protector, to try to persuade Moscow to drop support for him.
"As we continue to pursue the political option the realities on the ground may have overtaken us, therefore I think the clock is ticking and have we ... reached the point where the political option is too late?" King Abdullah of Jordan said in an interview with CNN.
"I think we should continue to give politics its due, but if we haven't already passed that window I think we are getting very close to it."