Syrian troops commanded by the brother of President Bashar al-Assad and backed by helicopter gunships have driven rebel fighters out of a district of Damascus a week after the insurgents launched a major assault on the capital.
Jihad Makdissi, spokesperson for the Syrian foreign ministry, said on Monday that the situation in Damascus was improving and would return to normal within days.
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Concerning the country's chemical weapons stocks, he said they are secure and would only be used in the case of an by foreign powers.
Makdissi told a news conference broadcast on state television that the weapons are under the protection of the Syrian army and would never be used "inside Syria".
Members of the Syrian army's Fourth Division under the command of Maher al-Assad executed several young men on the weekend during the operation to regain control of the northern Damascus district of Barzeh, a witness and activists said.
Government forces have launched a determined fightback since rebels brought their battle to overthrow Assad to the capital and killed four of the president's closest associates in a bomb attack on a meeting of senior security officials last Wednesday.
Activists told Al Jazeera that the military was sending reinforcements into the Syrian capital. The army has set up new checkpoints on one of the main roads into the city, they said.
In a further escalation of a conflict rapidly becoming a civil war, fighting raged around the intelligence headquarters in Syria's biggest city, Aleppo, and in Deir Az Zor in the east.
Jad Al Halabi, an activist in Syria's largest city Aleppo, said fighting in that city is the worst to date.
“I travelled to Salahedin neighbourhood. I was shocked to see the revolution flags everywhere, in the streets, on buildings, at the balconies. I also saw a large number of Free Syrian Army members,” he said by phone.
Syrian forces regained control of one of two border crossings seized by rebels on the frontier with Iraq, Iraqi officials said, but rebels said they had captured a third border crossing with Turkey: Bab al-Salam, north of Aleppo.
"Seizing the border crossings does not have strategic importance but it has a psychological impact because it demoralises Assad's force," a senior Syrian army defector in Turkey, Staff Brigadier Faiz Amr, told the Reuters news agency by phone.
"It's a show of progress for the revolutionaries, despite the superior firepower of Assad's troops."
Rebels also seized an army infantry school in the town of Musalmiyeh, 16km north of Aleppo, and captured several loyalist officers, while others defected, a senior military defector in Turkey and rebel sources inside Syria said.
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"This is of big strategic and symbolic importance. The school has ammunition depots and armoured formations and it protects the northern gate to Aleppo," Brigadier General Mustafa al-Sheikh said by phone from the town of Apayden on the Turkish border.
The bombardments in Damascus and Deir Az Zor were some of the fiercest yet and showed Assad's determination to avenge the bomb attack, the most spectacular blow in a 16-month-old uprising against four decades of rule by the Assad family.
Rebels were driven from Mezzeh, the diplomatic district of Damascus, residents and opposition activists said, and more than 1,000 government troops and allied militiamen poured into the area, backed by armoured vehicles, tanks and bulldozers.
Three people were killed and 50 others, mostly civilians, were wounded in the early morning bombardment, said Thabet, a Mezzeh resident. "The district is besieged and the wounded are without medical care," he said.
"I saw men stripped to their underwear. Three buses took detainees from al-Farouk, including women and whole families. Several houses have been set on fire."
'Safe passage for Assad'
Opposition and rebel sources say the guerrilla fighters in the capital may lack the supply lines to remain there for long and may have to make tactical withdrawals.
The neighbourhood of Barzeh, one of three northern areas hit by helicopter fire, was overrun by troops commanded by Maher al-Assad, 41, who is widely seen as the muscle maintaining the Assad family's Alawite minority rule.
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Syrian state television quoted a media source denying that helicopters had fired on the capital. "The situation in Damascus is normal, but the security forces are pursuing the remnants of the terrorists in some streets," it said.
Most shops in Damascus were closed and there was only light traffic - although more than in the past few days. Some police checkpoints, abandoned earlier in the week, were manned again.
Many petrol stations were closed, having run out of fuel, and those that were open had huge lines of cars waiting to fill up. Residents reported long queues at bakeries.
Elsewhere, Iraqi officials said Syrian forces had regained control of the Syrian side of the Yarubiya border crossing, briefly seized by rebels on Saturday. Iraq has said it cannot help Syrians fleeing the violence, and the border was sealed by the Iraqi army on Friday.
Arab League ministers meeting in Doha urged the opposition and the rebel Free Syrian Army to form a transitional government, Qatari Prime Minister Sheikh Hamad bin Jassim al-Thani told a news conference in Doha.
He said Arab countries would help to ensure safe passage out of Syria for Assad if he stepped down quickly - something he has shown no inclination to do.