BEIRUT (AP) - Fighter jets unleashed sonic booms and helicopter gunships strafed rebels as they pressed their fight Tuesday into new neighborhoods in Aleppo, Syria's largest city. Farther south, ground troops combed Damascus after the nearly complete rout of the largest rebel assault yet on the capital.
After a series of setbacks, President Bashar Assad's forces are solidifying their grip on Aleppo and Damascus, knowing their fall would almost certainly spell the regime's end.
The regime appears to be regaining momentum after a series of setbacks that put it on the defensive. But while its forces easily outgun the rebels in direct confrontations, the rebellion has spread them thin - pointing to a drawn-out civil war.
Syria's two biggest cities, home to more than one-third of the country's 22 million people and centers of its political and economic life, have remained largely insulated from the unrest that has ravaged much of the rest of the country during the 16-month conflict.
But this month, rebels from surrounding areas have pushed into both, bringing street battles to previously calm urban neighborhoods.
The fighting in each city has followed a similar script.
After building up their forces in the countryside and clashing with government troops there, rebels pressed into Damascus early last week, sparking clashes around the city with government troops.
The opposition landed a harsh blow July 18, when a bomb tore through a high-level security meeting, killing four top Assad security advisers including his minister of defense and his older sister's husband. All had been key architects of the government's efforts to quash the uprising.
But the battle turned when the regime deployed the overwhelming force it has used to crush rebels elsewhere, shelling residential areas and targeting rebels with machine guns and missiles fired from attack helicopters.
On Tuesday, the government appeared to have largely retaken the capital. Activists reported shelling and sporadic clashes between troops and rebels in and around the city, but acknowledged most fighters had withdrawn.
While the regime asserted control in the capital, rebels in the north launched an assault on Aleppo over the weekend. They pushed into neighborhoods in the southern and northeastern edges of the city and destroyed at least three government tanks.
The fighting expanded on Tuesday, with clashes spreading into neighborhoods on two sides of the historic old city and into a number of other areas, activists said.
The government fought back much as it did in Damascus, firing artillery shells on rebel areas and pursuing fighters with attack helicopters. Residents also reported fighter jets swooping over the city, breaking the sound barrier to cause sonic booms in a show of force.
"It's the worst day of fighting in Aleppo so far, but I can't tell what's happening on the ground or who's in control," said a local writer who spoke on condition of anonymity for fear of reprisals. "This is bad because in the end it's the civilians who will pay the price of this street fighting."
Prisoners in Aleppo's jail also rioted overnight, and activists said government forces killed at least eight of them. Guards quelled another prison riot in the nearby city of Homs with tear gas and live ammunition.
In Israel, which shares a closed and hostile border with Syria, the military chief warned his own government that an Israeli attack on Syria's chemical weapons depots could drag the Jewish state into a broader war.
Israeli officials have expressed fears that chaos in Syria could allow non-conventional weapons to reach those who would use them against Israel.
Israel must move cautiously to avoid "a broader offensive than we planned," Lt. Gen. Benny Gantz said, according to the army's website.