The Syrian defence minister has been killed and several other senior security officials wounded after a suicide bomber struck the National Security building in Damascus during a meeting of cabinet ministers and senior security officials.
State television confirmed General Daoud Rajha was killed in Wednesday's suicide blast and that several other participants in a top-level meeting who were wounded in the blast had been rushed to Al-Shami hospital in the capital.
Al Jazeera's Rula Amin, reporting from Beirut, capital of neighbouring Lebanon, said: "We don't know yet the number of casualties but the fact that it happened near where the president lives is significant."
The explosion came as clashes beween the Syrian military and the Free Syrian Army in Damascus entered a fourth straight day.
Citing the UK-based Syrian Observatory for Human Rights, news agencies reported sounds of explosions on the outskirts of the Syrian capital on Wednesday.
Fighting was also reported in the central district of al-Midan, where rebel fighters are holed up.There were no immediate reports of casualties.
More government forces and tanks were deployed in areas inside and around Damascus following the violence, activists said.
The SOHR also said that more than 60 soldiers had been killed in clashes with the FSA fighters in the past 48 hours, but there was no independent confirmation of the claim as foreign media is barred from reporting inside Syria.
"Between 40 and 50 soldiers of the regular Syrian forces were killed the day before yesterday [Monday] in fighting in Damascus, and at least 20 were killed yesterday," the Observatory's Rami Abdel Rahman told the AFP news agency.
He added that forces of the presidential guard had deployed around the capital, but "they are not involved in the fighting" that erupted in several districts of the city on Sunday.
Soldiers loyal to al-Assad have called on civilians in Damascus areas controlled by the rebels to "leave immediately" ahead of an attack to purge those areas of "terrorists", activists said.
The rebels said on Tuesday they had intensified their offensive, declaring the latest phase of their offensive would "liberate" Damascus. A rebel spokesman said "victory is nigh".