Syria has rejected a call by the Arab League for President Bashar al-Assad to give up power.
"We are sorry that the Arab League has descended to this level concerning a member state of this institution," foreign ministry spokesman Jihad Makdissi said at a media conference on Monday. "This decision only concerns the Syrian people, who are the sole masters of fate of their governments."
"If the Arab nations who met in Doha were honest about wanting to stop the bloodshed they would have stopped supplying arms... they would stop their instigation and propaganda," Makdissi said. "All their statements are hypocritical."
The Arab League on Monday called on Assad to swiftly step aside in order to end the fighting that has swept across the country.
"There is agreement on the need for the rapid resignation of President Bashar al-Assad," Qatar's Prime Minister Hamad bin Jassem al-Thani told journalists at the end of the ministerial meeting in Doha.
The Arab League also urged the rebel Free Syrian Army to form a transitional government of national unity.
"We call on the opposition and the Free Syrian Army to form a government of national unity," Sheikh Hamad said as he delivered the results of the Arab League meeting.
He urged Assad to take the "courageous" decision in order to save his country where fierce fighting continued to rage between government troops and rebels.
At the foreign ministry media conference, the Syrian government acknowledged for the first time that it possessed stockpiles of chemical and biological weapons and said it will only use them in case of a foreign attack and never internally against its own citizens.
"No chemical or biological weapons will ever be used, and I repeat, will never be used, during the crisis in Syria no matter what the developments inside Syria," spokesman Makdissi said.
"All of these types of weapons are in storage and under security and the direct supervision of the Syrian armed forces and will never be used unless Syria is exposed to external aggression."
In a sign that Iran, Syria's main ally in the region, is acknowledging the pressure on the Assad government, its parliamentary speaker proposed on Monday that Syria hold presidential elections as a way to end the civil war.
Ali Larijani told Iran's state-run Arabic language Al-Alam TV on Monday that presidential elections in Syria could be held while planning future parliamentary elections. He said fighting in Damascus and elsewhere has blocked an attempt to organise voting and that Assad's government backs the idea.
The statement came as 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.
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.
In-depth coverage of escalating violence across Syria
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.
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.
"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.
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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.
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.