Syria crisis: Fighting in Aleppo amid rebel offensive
Fierce fighting is taking place in Syria's second city, Aleppo, say reports, as rebel fighters try to take control from the army.
Pro-government troops are bombarding the city with shells and rocket fire, and there are reports that helicopter gunships are being used.
Activists say at least 33 people have been killed across the country on Tuesday so far.
Nine of those are reported to have died during a prison revolt in Aleppo.
Syrian state television says the government has now regained control of most areas of Damascus which had been captured by rebels last week.
It broadcast footage showing soldiers apparently securing and checking heavily shelled suburbs in southern Damascus and the bodies of "terrorists" it says were killed.
But a fierce battle is taking place for control of Aleppo, Syria's commercial centre, after rebels launched a major offensive at the weekend.
Heavy shelling and rocket fire were reported overnight and into Tuesday as the government attempted to take back the seized districts. Residents and activists told Reuters news agency the two sides were battling close to the historic Old City.
The British-based Syrian Observatory for Human Rights said helicopter gunships had fired on several districts of the city.
The BBC's Wyre Davies, on the Turkish border with Syria, says losing Aleppo would be a serious blow to the government so it is determined to use its far superior weaponry to halt the rebels' advance.
Activists say at least nine people have died in the revolt in Aleppo prison, where security forces are reported to have opened fire and used tear gas on detainees.
Explosions and fires have also been reported from the jail in the city of Homs, where unarmed policemen are said to have defected and prisoners have staged a sit-in.
Government officials had previously denied there had been a defection.
The activist group the Local Co-Ordination Committee (LCC) said there was a "catastrophic humanitarian situation" inside the Homs jail.
The group called for international help to prevent "mass executions" of prisoners.
The Observatory, which said two prisoners were killed at the jail on Saturday, said it had received reports that a group of judges had been sent to the jail to investigate the uprising, which began over the weekend.
"It is possible their presence might lead to summary executions," the head of the Observatory, Rami Abdel Rahman, told AFP.
The group says that, on Monday, more than 116 people were killed across Syria, and that at least 33 had died by early afternoon on Tuesday. More than 1,260 civilians, rebels and government soldiers have died since the fighting in Damascus and elsewhere intensified on 15 July, it says.
Foreign journalists work under intense restrictions in Syria so reports by both sides are hard to verify.
In other developments
- President Assad named internal security head Gen Ali Mamlouk as his new head of national security, replacing Hisham Bekhtyar, one of four senior officials killed in the 18 July bombing in Damascus
- A commander of Iran's Revolutionary Guards, Brig Gen Masoud Jazayeri, said "decisive blows" would be struck against Syria's enemies, "particularly the hated Arabs", if they intervened in the conflict, Iran's semi-official Fars news agency reported.
The surge in fighting in Syria coincides with widespread concern over Syria's stockpile of chemical weapons.
Both the US and UN gave clear warnings to Damascus after an official said on Monday that while such weapons would not be deployed inside Syria they could be used in response to external aggression.
Israel and the US are concerned the weapons could fall into the hands of Lebanon's Shia Islamist group Hezbollah, allied to Syria's President Bashar al-Assad, and be used to threaten Israel.
A senior Israeli defence official, Amos Gilad, said the weapons were "under the full control of the regime", Reuters news agency reports.
The FSA said in a statement on Tuesday that the government had begun moving its chemical weapons stockpile to airports on Syria's border a few months ago, in an attempt to put pressure on the international community.
On Sunday, the Syrian Observatory for Human Rights reported that at least 19,106 people had been killed since March 2011. The UN said in May that at least 10,000 people had been killed.
Syria blames the violence on foreign-backed "armed terrorist gangs".
In June, the Syrian government reported that 6,947 Syrians had died, including at least 3,211 civilians and 2,566 security forces personnel.