Syrian troops and tanks on Friday drove rebels from a Damascus neighbourhood where some of the heaviest of this week's fighting in the capital left cars gutted and fighters' bodies in the streets.
More than 200 people were killed across the country in a single day, activists said on Friday, as the military struggled to regain momentum after a stunning bombing against the regime's leadership.
A fourth member of President Bashar al-Assad's inner circle, national security chief General Hisham Ikhtiyar, died of wounds he suffered in Wednesday's bomb blast, which went off during a high-level security meeting
in Damascus, according to government media.
The bombing has been described as a resounding blow to Assad, killing his defence minister and his influential brother-in-law along with another security official, all central to directing the crackdown on the uprising against his rule.
The blast, six days of sustained fighting in neighbourhoods across central districts of the capital and the fall of several border posts into rebel hands appear to point to the unravelling of Assad's grip on power.
Regime troops regained control of the district of Midan in the southern part of Damascus on Friday. But rebels launched new fighting in several other districts of the capital, activists said.
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Battles involving troops bringing in tanks, helicopters and mortars have turned parts of Damascus into combat zones, according to witnesses, and sent thousands of Syrian families packed in cars streaming across the border into neighbouring Lebanon.
"Our heroic forces have completely cleansed the Midan area of the terrorist mercenaries," state TV announced, employing the term used by authorities to refer to rebels.
It said authorities seized large quantities of weapons including machine guns, explosive belts, rocket-propelled grenades and communications equipment.
Damascus activist Khaled al-Shami said rebels carried out a "tactical" retreat early on Friday to spare civilians further shelling after five days of intense clashes between opposition fighters and regime forces.
Rebels continued to strike elsewhere in the capital on Friday. Rebels attacked a police station on Khaled bin Waleed Street, where heavy fighting was going on, the Britain-based Syrian Observatory for Human Rights said.
Clashes were also reported in the northern Barzeh and Rukneddine districts.
A Syria-based activist who goes by the name of Bashir al-Dimashqi said the rebels in Damascus were staging hit and run attacks and striking at security targets as opposed to controlling areas.
"Their strategy is to paralyse public institutions and chip away at the regime," he said.
Activists reported that 310 people were killed in violence nationwide on Thursday, making it the single deadliest day of fighting since the revolt began.
Besides the fighting in Damascus on Friday, about a half-dozen rebels took over a Syrian border crossing near the Iraqi town of Qaim on Thursday, said Iraqi army Brigadier General Qassim al-Dulaimi. There are four major border posts with Iraq.
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Rebels overtook a Syrian army outpost near the Syrian-Iraq border after clashes that killed 21 Syrian soldiers, he added.
In addition, amateur video posted online showed rebels taking over the Bab al-Hawa border crossing with Turkey, where they stomped on portraits of Assad. The footage could not be independently verified.
A Turkish official based in Reyhanli, on the Turkish side of the border gate of Bab al-Hawa, confirmed that the rebels had taken control of the frontier crossing, and Al Jazeera could confirm on Saturday that the crossing remained in the hands of the rebels.
Al Jazeera's Isil Sariyuce, reporting from the Turkish side of the border, said on Friday that the border crossing is "important strategically and symbolically" for the Free Syrian Army.
"If they can control it, it will be easier to control the supply lines to their fighters, and it is the main transit point between Turkey and Syria."