Fierce fighting erupted on Saturday in Syria's historic northern city of Aleppo, with thousands of residents forced to flee amid bloody clashes between resurgent Free Syrian Army fighters and government troops.
Activists posted video showing residents fleeing Aleppo in cars and minibuses early on Saturday, after the authorities warned that they would shell rebel-controlled districts. Most of the fighting was in the Salaheddin part of the city, they said, where FSA fighters were massing.
Aleppo, Syria's second largest city, is dominated by Sunni Muslims, but has a minority population of Christians of various denominations.
It had so far largely escaped the country's 16-month conflict, which has recently become a fast-changing guerrilla war between opposition fighters and the Syrian army, which has heavy weapons.
The battle in Aleppo comes after a devastating week for the president, Bashar al-Assad, with fighting in the heart of the capital, Damascus; a bomb attack that killed four members of his military-security command; and predictions that his regime was entering its final weeks or months.
Assad's forces continue to control key cities, at least during the day, but have lost much of the rural hinterland. The FSA has been able to capture a series of border posts with Turkey and Iraq, further puncturing the regime's authority, and is now controlling large areas of the northern and eastern periphery.
The FSA had previously reached within nine miles of Aleppo. On Saturday activist Mohammad Saeed said that dozens of FSA rebels had penetrated deep inside the city. There were reports that they had set up checkpoints in some areas. Video showed thick black smoke billowing over buildings. Some residents had painted walls with the pre-Baathist flag, the symbol of the revolution.
In a further sign of rapid regime erosion, four more army brigadiers were said to have crossed into Turkey, bringing the number of senior military defectors there to about 100. Another brigadier, Adelnasser Ferzat, defected to FSA fighters in Aleppo, it was claimed. In a video address in fluent Russian, he urges Moscow to dump Assad and back "freedom" and the rebels' side.
Activists said that as many as 7,000 Aleppo residents have fled to safety. Last week's surge in violence has trapped millions of Syrians, with several areas of Damascus now deserted, and tens of thousands of refugees flooding into neighbouring Lebanon. Some 30,000 Syrians – many of them affluent – crossed the border into Lebanon on Thursday and Friday.
Diplomatic efforts to solve the crisis have been largely overtaken by events, despite a vote in the UN security council late on Thursday to extend the UN's monitoring mission for 30 days. The international community remains divided. Iran, Russia and China steadfastly support the Assad regime; Saudi Arabia and Qatar are overtly aiding the rebels; Britain, the US and the EU are calling for a "political transition" and Assad's immediate departure. Meanwhile, Israel, the region's most formidable military power, announced that it would consider action to prevent Syria's chemical weapons and missiles arsenal from falling into the hands of Hezbollah, Assad's Shia Islamist allies in neighbouring Lebanon.
Israel's defence minister, Ehud Barak, said: "I have instructed the military to increase its intelligence preparations and prepare what is needed so that ... [if necessary] ... we will be able to consider carrying out an operation."